What do Ammeters Measure?

The types of capacitors vary by design and application, including ceramic, electrolytic, film, and supercapacitors. Each offers unique benefits for electronics, power supply circuits, energy storage, and filtering needs.

What are the types of capacitors?

The types of capacitors are classified by material, function, and performance, serving vital roles in electronics and electrical systems.

✅ Ceramic, electrolytic, film, and supercapacitors used in diverse applications

✅ Store and regulate electrical energy in circuits, power systems, and devices

✅ Enable filtering, smoothing, and energy storage for stable performance

There are various types of capacitors. They are electronic components of electric filters and tuned circuits that store and release electrical energy. They consist of two conductive plates separated by a dielectric material. When a voltage is applied across the plates, an electric field is created between them, and an electrical charge accumulates on the plates. It represents the distance between the plates. The capacitance of a polarized capacitor is a measure of its ability to store electrical charge. To fully understand how capacitance works in different circuits, it is essential to study the various types and their dielectric materials.

These are widely used in electronic circuits, performing various functions such as filtering, smoothing, coupling, and timing. They can be found in everything from simple electronic devices like flashlights and radios to complex systems such as computers and spacecraft. A solid foundation in basic electricity helps explain why capacitors store and release energy depending on voltage and plate separation.

They come in many different types and sizes, each with unique properties that make them suitable for other applications. The most common types include ceramic, electrolytic, tantalum, film, and supercapacitors.

Engineers often compare capacitance in parallel with capacitance in series to determine how different capacitor arrangements affect circuit behavior.

Schematic symbols for a fixed and variable capacitor.

Ceramic

Ceramic capacitors use ceramic as their dielectric material and are ideal for high-frequency applications. They are available in different types, such as class 1 and class 2. Class 1 caps are used in circuits that require high precision and stability, while class 2 types of capacitors are used in circuits that require high capacitance values. In addition, ceramic caps are commonly used in decoupling, bypassing, and coupling applications.

Electrolytic

Electrolytic caps use an electrolyte as their dielectric material and are polarized. They are known for their high capacitance values and are commonly used in power supply circuits. There are two types of electrolytic caps: aluminum electrolytic caps and tantalum electrolytic caps. Aluminum electrolytic types of capacitors are inexpensive and have a high capacitance value, while tantalum electrolytic caps have higher stability and lower leakage current. Electrolytic caps are commonly used in DC blocking, coupling, and filtering applications.

Film

Film capacitors use a thin plastic or polymer layer as their dielectric material. They are known for their high stability and low losses, which are ideal for high-frequency applications. Film caps come in different types, such as metalized and film/foil, each with unique characteristics. Metalized film caps are used in circuits that require high capacitance values, while film/foil caps are used in circuits that require high precision and stability. Film caps are commonly used in decoupling, coupling, and filtering applications.

Tantalum

Tantalum capacitors are polarized caps that use tantalum metal as their anode. They are known for their high stability and are commonly used in low-voltage applications. Tantalum caps are available in tantalum foil caps and tantalum polymer caps. Tantalum foil caps are known for their high reliability. They are commonly used in aerospace and military applications, while tantalum polymer caps are known for their high capacitance values and low ESR, making them ideal for portable devices.

Mica

Silver mica capacitors use mica as their dielectric material and are known for their high precision, low losses, and excellent stability. They are used in various RF circuits, filters, and timing applications. Mica caps are available in different types, such as silver mica caps and ceramic mica caps. Silver mica caps are known for their high precision and stability. They are commonly used in RF circuits, while ceramic mica caps are known for their high capacitance values and low cost.

Oil

Variable Types

Variable caps are used in electronic circuits where the capacitance value needs to be adjusted. They consist of two conductive plates separated by an air gap, and the capacitance value can be changed by adjusting the distance between the plates. For example, variable caps are commonly used in radio tuning circuits and frequency control circuits.

Supercapacitors

Supercapacitors, also known as ultracapacitors, are a type of capacitor that has a higher energy storage capacity than other types. They are commonly used in applications where high power delivery is needed, such as in electric vehicles and renewable energy systems. They have a higher energy density than electrolytic caps and can be charged and discharged quickly, making them ideal for applications with a quick power boost.

Paper

Paper caps use paper as their dielectric material and are known for their high stability and low losses. Therefore, they are commonly used in filters, timing, and coupling applications. Paper caps are available in different types, such as oil-impregnated paper caps and metalized paper caps. Oil-impregnated paper caps are known for their high stability. Therefore, they are commonly used in high-voltage applications, while metalized paper caps are known for their high capacitance values and low cost.

Power

Power capacitors like power electronics and motor drives are designed for high voltage and high current applications. They are available in different types, such as film and electrolytic, each with unique characteristics. Power caps are known for their high reliability and low losses, making them ideal for high-power applications.

Frequently Asked Questions

What is an electrolytic capacitor, and how is it used?

An electrolytic capacitor is a type of capacitor that uses an electrolyte to achieve a more considerable capacitance value than other types. They are commonly used in power supply circuits due to their high capacitance values and ability to handle high voltages. Electrolytic caps have a polarized design and need to be installed with the correct polarity. Otherwise, they can fail or even explode due to the working voltage ratings. The unit of capacitance, measured in farads, is explained in more detail on our unit of capacitance page, along with practical examples. When comparing passive components, it is helpful to explore both the types of resistors and the types of caps to see how they complement each other in circuits.

How do ceramic capacitors differ?

Ceramic capacitors are a type of capacitor that uses a ceramic material as the dielectric. They are known for their high stability, low cost, and low leakage current. They can also operate at high temperatures due to their insulating layer.

What is a tantalum capacitor, and what are its advantages and disadvantages?

A tantalum capacitor is an electrolytic capacitor that uses tantalum as the anode material. They have a high capacitance per volume ratio and are commonly used in electronic circuits where space is limited. Tantalum ones also have a high level of stability and low leakage current. Additionally, they can operate at high temperatures due to the oxidized layer on the surface. However, they are more expensive than other types and can be sensitive to voltage spikes, which can cause them to fail.

What are film capacitors, and how are they used in electronic circuits?

Film capacitors are a type of capacitor that uses a thin film as the dielectric. They are known for their stability, low leakage current, and ability to operate at high frequencies. Film caps are commonly used in high-precision electronic circuits, such as audio equipment and signal processing circuits. The distance between the plates in a film capacitor represents the capacitance value.

What are the advantages and disadvantages of using supercapacitors?

Supercapacitors, also known as ultra, are a type of capacitor that has a much higher capacitance value than other types. As a result, they can store and release energy quickly and can handle many charge and discharge cycles. Additionally, they can operate at high temperatures. However, supercapacitors have a lower energy density than other types of energy storage devices, such as batteries, and can be more expensive due to their large capacitance.

How do variable capacitors differ from fixed capacitors?

Variable capacitors have a capacitance value that can be adjusted. They have commonly used in radio frequency (RF) circuits where the capacitance must be tuned to a specific frequency. Unlike fixed ones, variable ones have a moving plate that can be adjusted to change the capacitance value. They can also operate at high temperatures due to their insulating layer.

Related Articles

• Electricity Fundamentals

• Electricity Questions

• Electricity History

Low voltage refers to electrical systems operating at 50 to 1000 volts AC or 120 to 1500 volts DC. Common in residential, commercial, and control circuits, it reduces shock risks while powering lighting, HVAC, security systems, and automation equipment safely.

What is Low Voltage?

Low voltage is a range of electrical power levels below high-voltage thresholds.

✅ Reduces risk of electrical shock in residential and commercial settings

✅ Powers lighting, security, HVAC, and control systems

✅ Common in telecommunications and automation applications

In today's technologically driven world, understanding the concept of low voltage (LV) is essential. Low voltage systems are widely used across industries, homes, and offices, making them an integral part of our daily lives. This article provides an overview of LV, its applications, safety measures, and regulations, incorporating the keywords provided. Low voltage systems are designed to operate below 600 volts, unlike high voltage systems that present increased shock hazards.

The low voltage definition is relatively simple: Any electrical system or equipment operating at a voltage level less than or equal to 600 volts. LV systems in the United States are generally categorized as those working between 50 and 600 volts. These systems are utilized in various applications due to their low power consumption and reduced risk of electric shock. Understanding the concept of voltage is essential when working with residential or industrial low voltage wiring.

Applications

Low voltage applications are diverse and include control rooms, distribution systems, lighting, communication systems, and security systems. LV wiring is often used in these applications, as it is designed for smaller currents and offers increased safety compared to regular wiring. This wiring type is also more cost-effective and easier to install. Voltage drop can significantly impact the performance of low voltage circuits, especially over long wiring runs.

Regarding LV safety, it is crucial to take necessary precautions as even LV electrical equipment can pose risks. For example, to minimize the chance of electric shock, one should always turn off the power supply before working on any electrical equipment and use insulated tools. Additionally, it is essential to adhere to local LV regulations and standards to ensure a safe working environment.

Devices

Low voltage devices are found in various settings, from residential to commercial and industrial. Some examples of low voltage devices include thermostats, doorbells, intercom systems, and landscape lighting. These devices usually require transformers to convert the higher voltage from the main power supply to a lower voltage suitable for operation.

Regulations and standards for LV installations vary by country and region. However, the National Electrical Code (NEC) provides guidelines and requirements for LV installations to ensure safety and reliability in the United States. Professionals working with low voltage systems must adhere to these guidelines and any additional local regulations.

Low voltage transformers and power supplies are critical in distributing low voltage electricity. Transformers are used to step down higher voltages from the main power supply to the required LV level. In contrast, power supplies regulate and distribute electrical energy to various devices. Low voltage distribution systems are designed to efficiently deliver electricity to low voltage equipment while maintaining safety and reliability.

Systems

While low voltage systems are generally safer than high voltage electrical systems, they still require proper handling and adherence to safety measures. High-voltage transmission systems are used to transport electricity over long distances from power plants to substations. High voltages range from 100 kV to 765 kV, while ultra-high voltages can reach above 800 kV. Large industrial facilities, such as factories that use medium-voltage systems, typically operate between 1 kV and 35 kV.

Understanding LV is crucial today, as these systems are widely used in various applications. With proper installation, adherence to regulations, and safety precautions, LV systems can provide numerous devices with an efficient and reliable power supply. As a result, low voltage systems play an essential role in our daily lives, whether for lighting, communication, or security. Key electrical components such as resistors and capacitors are frequently used in low voltage control systems.

Frequently Asked Questions

Is "low voltage" defined differently in 110V systems and 220V systems?

While the term "low voltage" describes electrical systems operating at a voltage level lower than a certain threshold, the specific voltage ranges considered low voltage can vary slightly between countries and regions due to differences in their electrical distribution systems. However, the general concept remains the same across 110V systems in North America and 220V systems in the EU. For efficient power distribution, low voltage systems rely on solid grounding practices, making ground faults and electrical faults important safety considerations.

In North America, low voltage typically refers to electrical systems operating between 50 and 600 volts. In contrast, in the EU, the term "LV" is defined by the Low Voltage Directive (LVD), which covers electrical equipment designed for use with a voltage rating of 50 to 1000 volts for alternating current (AC) and 75 to 1500 volts for direct current (DC).

Despite these minor differences in the defined voltage ranges, the reasons behind the classification of LV systems remain consistent. LV systems are generally considered safer than their high voltage counterparts, as the risk of electric shock is lower. Additionally, they consume less power, making them more energy-efficient and cost-effective for certain applications.

The main factor causing the difference in voltage levels between regions is the choice of electrical distribution systems. For example, 110-120V systems are more common in North America, while in Europe and many other parts of the world, 220-240V systems are standard. This difference is primarily due to historical reasons and the evolution of each region's electrical infrastructure over time.

Regardless of these regional differences in voltage levels, the fundamental principles and safety considerations for LV systems remain largely the same. Both 110V and 220V systems use LV electrical equipment and wiring to provide power for various applications while adhering to regional safety standards and regulations to ensure these systems' safe and efficient operation. The behavior of current in low voltage applications is best understood by applying Ohm’s Law, which explains the relationship between voltage, current, and resistance.

What are examples of low voltage systems?

Low voltage systems are widely used in various residential, commercial, and industrial applications due to their increased safety and energy efficiency. Here are some examples of LV systems:

Lighting systems: Low voltage lighting, such as LED lights and halogen lamps, is commonly used for residential and commercial purposes, including landscape lighting, recessed lighting, and track lighting. These systems often use transformers to step down the voltage from the main power supply to a suitable level for the lights.

Security systems: LV is used in security systems, including alarm systems, access control systems, and surveillance cameras. These systems require a stable and reliable power source with minimal risk of electrical hazards.

Communication systems: LV wiring is utilized in various communication systems, including intercoms, telephone lines, and data networks. It enables the reliable transmission of data and voice signals while minimizing energy consumption and interference.

Audio and video systems: LV components are used in home theatre systems, speakers, and AV equipment. The low voltage wiring ensures minimal signal loss and interference for better audio and video quality.

HVAC controls: Thermostats, sensors, and control panels for heating, ventilation, and air conditioning systems often use low voltage wiring and components to maintain efficient energy use and reliable control of the HVAC system.

Doorbells and chimes: LV systems are commonly used in doorbells and chime systems to ensure safe and reliable operation.

Fire alarm systems utilize LV wiring and components to provide a reliable means of detecting and responding to potential fire hazards while minimizing the risk of electrical hazards.

Home automation systems often utilize LV for controlling and automating various devices, including lighting, appliances, and security systems. This allows for the energy-efficient and safe operation of connected devices.

Solar power systems: In small-scale solar power installations, LV DC systems are used to store and distribute the electricity generated by solar panels. These systems typically include charge controllers, batteries, and inverters to efficiently manage the power supply.

Industrial control systems: LV is used in various industrial applications to control and monitor machinery and equipment. This includes programmable logic controllers (PLCs), motor controls, and sensor networks, which require stable and reliable power sources with minimal risk of electrical hazards. Devices like multimeters and voltmeters are essential tools for testing and maintaining low voltage installations.

Related Articles

• Electricity Fundamentals

• Electricity Questions

• Electricity History

Voltage is the electrical potential difference between two points, providing the force that moves current through conductors. It expresses energy per charge, powering devices, controlling circuits, and ensuring efficient and safe operation of electrical and electronic systems.

What is Voltage?

Voltage is the electric potential difference, the work done per unit charge (Joules per Coulomb). It: 

✅ Is the difference in electric potential energy between two points in a circuit.

✅ Represents the force that pushes electric current through conductors.

✅ It is measured in volts (V), and it is essential for power distribution and electrical safety.

To comprehend the concept of what is voltage, it is essential to understand its fundamental principles. Analogies make this invisible force easier to picture. One of the most common is the water pressure analogy: just as higher water pressure pushes water through pipes more forcefully, higher voltage pushes electric charges through a circuit. A strong grasp of voltage begins with the fundamentals of electricity fundamentals, which explain how current, resistance, and power interact in circuits.

Another way to imagine what is voltage is as a hill of potential energy. A ball placed at the top of a hill naturally rolls downward under gravity. The steeper the hill, the more energy is available to move the ball. Likewise, a higher voltage means more energy is available per charge to move electrons in a circuit.

A third analogy is the pump in a water system. A pump creates pressure, forcing water to move through pipes. Similarly, a battery or generator functions as an electrical pump, supplying the energy that drives electrons through conductors. Without this push, charges would remain in place and no current would flow.

Together, these analogies—water pressure, potential energy hill, and pump—show how voltage acts as the essential driving force, the “electrical pressure” that enables circuits to function and devices to operate. Since voltage and Current are inseparable, Ohm’s Law shows how resistance influences the flow of electricity in every system.

These analogies help us visualize voltage as pressure or stored energy, but in physics, voltage has a precise definition. It is the work done per unit charge to move an electric charge from one point to another. Mathematically, this is expressed as:

V = W / q

where V is voltage (in volts), W is the work or energy (in joules), and q is the charge (in coulombs). This equation shows that one volt equals one joule of energy per coulomb of charge.

In circuit analysis, voltage is also described through Ohm’s Law, which relates it to current and resistance:

V = I × R

where I is current (in amperes) and R is resistance (in ohms). This simple but powerful formula explains how voltage, current, and resistance interact in every electrical system.

Italian physicist Alessandro Volta played a crucial role in discovering and understanding V. The unit of voltage, the volt (V), is named in his honor. V is measured in volts, and the process of measuring V typically involves a device called a voltmeter. In an electrical circuit, the V difference between two points determines the energy required to move a charge, specifically one coulomb of charge, between those points. The history of voltage is closely tied to the History of Electricity, where discoveries by pioneers like Volta and Franklin have shaped modern science.

An electric potential difference between two points produces an electric field, represented by electric lines of flux (Fig. 1). There is always a pole that is relatively positive, with fewer electrons, and one that is relatively negative, with more electrons. The positive pole does not necessarily have a deficiency of electrons compared with neutral objects, and the negative pole might not have a surplus of electrons compared with neutral objects. But there's always a difference in charge between the two poles. So the negative pole always has more electrons than the positive pole.

Fig 1. Electric lines of flux always exist near poles of electric charge.

The abbreviation for voltage measurement is V. Sometimes, smaller units are used. For example, the millivolt (mV) is equal to a thousandth (0.001) of a volt. The microvolt (uV) is equal to a millionth (0.000001) of a volt. And it is sometimes necessary to use units much larger than one volt. For example, one kilovolt (kV) is equal to one thousand volts (1,000). One megavolt (MV) is equal to one million volts (1,000,000) or one thousand kilovolts. When comparing supply types, the distinction between Direct Current and AC vs DC shows why standardized voltage systems are essential worldwide.

The concept of what is voltage is closely related to electromotive force (EMF), which is the energy source that drives electrons to flow through a circuit. A chemical battery is a common example of a voltage source that generates EMF. The negatively charged electrons in the battery are compelled to move toward the positive terminal, creating an electric current.

In power distribution, three-phase electricity and 3 Phase Power demonstrate how higher voltages improve efficiency and reliability.

Voltage is a fundamental concept in electrical and electronic systems, as it influences the behavior of circuits and devices. One of the most important relationships involving V is Ohm's Law, which describes the connection between voltage, current, and resistance in an electrical circuit. For example, Ohm's Law states that the V across a resistor is equal to the product of the current flowing through it and the resistance of the resistor. 

The voltage dropped across components in a circuit is critical when designing or analyzing electrical systems. Voltage drop occurs when the circuit components, such as resistors, capacitors, and inductors, partially consume the V source's energy. This phenomenon is a crucial aspect of circuit analysis, as it helps determine a system's power distribution and efficiency. Potential energy is defined as the work required to move a unit of charge from different points in an electric dc circuit in a static electric field.  Engineers often analyze Voltage Drop to evaluate circuit performance, alongside concepts like Electrical Resistance.

Voltage levels are standardized in both household and industrial applications to ensure the safe and efficient operation of electrical equipment. In residential settings, common voltage levels range from 110 to 240 volts, depending on the country. Industrial applications often utilize higher voltages, ranging from several kilovolts to tens of kilovolts, to transmit electrical energy over long distances with minimal losses.

Another important distinction in the realm of voltage is the difference between alternating current (AC) and direct current (DC). AC alternates periodically, whereas DC maintains a constant direction. AC is the standard for most household and industrial applications, as it can be easily transformed to different voltage levels and is more efficient for long-distance transmission. DC voltage, on the other hand, is often used in batteries and electronic devices.

Voltage is the driving force behind the flow of charge carriers in electrical circuits. It is essential for understanding the behavior of circuits and the relationship between voltage, current, and resistance, as described by Ohm's Law. The importance of V levels in household and industrial applications, as well as the significance of voltage drop in circuit analysis, cannot be overstated. Finally, the distinction between AC and DC voltage is critical for the safe and efficient operation of electrical systems in various contexts.

By incorporating these concepts into our understanding of voltage, we gain valuable insight into the world of electricity and electronics. From the pioneering work of Alessandro Volta to the modern applications of voltage in our daily lives, it is clear that voltage will continue to play a crucial role in the development and advancement of technology. Foundational principles such as Amperes Law and the Biot Savart Law complement voltage by describing how currents and magnetic fields interact.

Related Articles

• Electricity Fundamentals

• Electricity Questions

• Electricity History

An electrical circuit is a closed loop that allows electric current to flow through conductors, power sources, and loads. Circuits connect electrical devices, enable energy transfer, and ensure safe operation in homes, industries, and power systems.

What is an Electrical Circuit?

An electrical circuit is a path through which electricity flows from a power source to one or more devices that are connected.

✅ Provides controlled current flow through conductors

✅ Powers electrical devices safely and efficiently

✅ Includes sources, loads, and protective components

Gaining a grasp of the basic electricity of electrical circuits, including series and parallel configurations, voltage, current, resistance, Ohm's Law, and circuit analysis techniques, is vital for anyone interested in electronics, electrical engineering, or the inner workings of modern technology.

Core Components & Function

In order to understand what an electrical circuit is, one must appreciate that, 

At its core, an electrical circuit is a closed loop or pathway that facilitates the flow of electric current. This concept is essential in electronics and electrical engineering, as it provides the basis for the operation of everyday items, including smartphones, computers, and home appliances.

Within an electrical circuit, components are connected via conductive materials, such as wires, which enable the movement of electrons from a power source to other components and back.

The primary components of an electrical circuit include a power source (e.g., a battery or power supply unit), conductive materials (typically wires), a load (such as a resistor, motor, or light bulb), and a control element (for example, a switch). The power source supplies the voltage necessary for electric current flow, while the load transforms electrical energy into other forms, such as light or heat. Meanwhile, the control element permits the user to initiate or halt the flow of electrons, effectively turning a device on or off.

• For students, a simple example is a battery connected to an LED, which demonstrates how electricity creates light.

• For professionals, an industrial motor powered by a control circuit shows how electrical energy drives large-scale equipment.

Circuit Types (Series vs. Parallel)

Electrical circuits can be classified into three main types: series, parallel, and combination circuits.

• Series circuits connect components end-to-end, allowing current to flow sequentially through each one. Example: holiday string lights, where a single bulb outage can disrupt the entire circuit.

• Parallel circuits enable current to flow through multiple paths. Example: household wiring, where turning off one light doesn’t affect others.

• Combination circuits mix both series and parallel configurations to handle more complex systems.

Fundamental Laws (Ohm’s Law, Kirchhoff’s Laws)

A fundamental understanding of voltage, current, and resistance is crucial for comprehending electrical circuit operations.

Voltage, the driving force that propels electric charge through a circuit, and current, the flow of electric charge measured in amperes (A), are closely related to resistance. Resistance, expressed in ohms (Ω), represents the opposition to the flow of current. These elements are interconnected through Ohm's law, which states that the voltage across a conductor is directly proportional to the current it carries and inversely proportional to its resistance: V = IR, where V represents voltage, I denotes current, and R represents resistance. Understanding how current creates magnetic fields is explained by Ampere's Law, which forms the basis for analyzing electromagnetism in electrical circuits.

Circuit analysis determines the current, voltage, and power associated with each component in an electrical circuit. Techniques such as Kirchhoff's Law of voltage and current, Thevenin's theorem, and Norton's theorem are employed to analyze and resolve electrical circuit issues. These methods enable engineers to design and troubleshoot electronic devices and systems effectively.

Thevenin's Theorem

Thevenin's theorem is a fundamental principle in electrical engineering and circuit analysis. It is a powerful technique to simplify complex linear circuits, making it easier to analyze and calculate the current, voltage, and power across specific components. The theorem is named after the French engineer Charles Léonard Siméon Thévenin, who proposed it in 1883.

Thevenin's theorem states that any linear, active, bilateral network containing voltage sources, current sources, and resistors can be replaced by an equivalent circuit consisting of a single voltage source (called Thevenin's voltage, Vth) in series with a single resistor (called Thevenin's resistance, Rth) connected to the terminals of the original circuit. This simplified circuit, known as the Thevenin equivalent circuit, can then be used to analyze the behaviour of the original circuit with a specific load connected to its terminals.

Steps to apply Thevenin’s theorem:

1. Identify the portion of the circuit you want to simplify and the terminals where the load will be connected.

2. Remove the load from the terminals (if present) and leave the terminals open-circuited.

3. Calculate the open-circuit voltage across the terminals. This value is Thevenin's voltage (Vth).

4. Calculate the equivalent resistance seen from the open-circuited terminals with all independent voltage sources replaced by short circuits (zero resistance) and all independent current sources replaced by open circuits (infinite resistance). This value is Thevenin's resistance (Rth).

5. Create the Thevenin equivalent circuit using the calculated Vth and Rth values, then connect the original load across the terminals.

Once the Thevenin equivalent circuit is determined, you can easily analyze the circuit's behaviour and calculate the current through the load, the voltage across the load, or even the power delivered to the load. This technique is particularly useful when analyzing circuits with varying loads or examining the circuit's behaviour at multiple points, as it simplifies calculations and saves time.

Norton’s Theorem

Norton's theorem is a fundamental principle in electrical engineering and circuit analysis that simplifies the analysis of complex linear circuits. Named after the American engineer Edward Lawry Norton, who introduced it in the early 20th century, the theorem is a counterpart to Thevenin's theorem.

While Thevenin's theorem reduces a complex network to an equivalent voltage source in series with a resistor, Norton's theorem simplifies the network to an equivalent current source parallel to a resistor.

Norton's theorem states that any linear, active, bilateral network containing voltage sources, current sources, and resistors can be replaced by an equivalent circuit consisting of a single current source (called Norton's current, IN) in parallel with a single resistor (called Norton's resistance, RN) connected to the terminals of the original circuit.

Steps to apply Norton’s theorem:

1. Identify the portion of the circuit you want to simplify and the terminals where the load will be connected.

2. Remove the load from the terminals (if present) and leave the terminals open-circuited.

3. Calculate the short-circuit current flowing between the terminals. This value is Norton's current (IN).

4. Calculate the equivalent resistance seen from the open-circuited terminals with all independent voltage sources replaced by short circuits (zero resistance) and all independent current sources replaced by open circuits (infinite resistance). This value is Norton's resistance (RN). Note that Norton's resistance is equal to Thevenin's, as both are calculated similarly.

5. Create the Norton equivalent circuit with the calculated IN and RN values, connecting the original load across the terminals.

Once the Norton equivalent circuit is established, you can easily analyze the circuit's behaviour and calculate the current through the load, the voltage across the load, or even the power delivered to the load. Like Thevenin's theorem, Norton's theorem is particularly useful when dealing with varying loads or analyzing a circuit's behaviour at multiple points. In addition, it simplifies calculations, conserving time and effort.

Circuit Diagrams & Symbols

Circuit diagrams, also known as schematic diagrams, are graphical representations of electrical circuits that utilize standardized symbols to depict components such as resistors, capacitors, inductors, diodes, and transistors. These symbols facilitate the interpretation of a circuit's structure and function by engineers or hobbyists without requiring physical examination of the actual components.

Here are some common symbols used in circuit diagrams:

Resistor: A simple zigzag line represents a resistor, which opposes the flow of electric current and dissipates energy in the form of heat.

Capacitor: Two parallel lines with a small gap represent a capacitor. The positive plate is marked with a "+" sign in polarized capacitors, and a curved line represents the negative plate.

Inductor: A series of curved or looped lines, similar to a coil, represents an inductor, which stores energy in a magnetic field and opposes changes in current.

Diode: A triangle pointing to a line represents a diode, which allows current to flow in one direction but blocks it in the opposite direction.

Light-emitting diode (LED): Similar to a diode symbol, but with two arrows pointing away from the triangle, representing light emission.

Transistor: Two types of transistors are commonly used: bipolar junction transistors (BJTs) and field-effect transistors (FETs). A BJT symbol comprises a circle or rectangle with three connected leads (emitter, base, and collector). FET symbols are represented by a combination of lines and a vertical arrow with three terminals (gate, source, and drain).

Integrated circuit (IC): A rectangular or square box with multiple leads connected represents an integrated circuit, a complex assembly of numerous electronic components within a single package.

Battery: Alternating long and short parallel lines represent a battery, a source of electrical energy.

Power supply: A circle with an arrow pointing upwards or a combination of letters, such as "Vcc" or "+V," represents a power supply, which provides a constant voltage or current.

Switch: A break in line with an angled line nearby or a pair of lines connected by a diagonal line represents a switch, which controls the flow of current by making or breaking a circuit.

Ground: A series of horizontal lines that decrease in length, a downward-pointing arrow, or the letters "GND" represent a ground connection, which serves as a reference point and provides a return path for electrical currents.

These are just a few examples of the many symbols used in circuit diagrams. Therefore, it's essential to familiarize yourself with these symbols to read or create schematic diagrams for electrical or electronic circuits. The ability of a circuit to store electrical charge is described by Capacitance, a key principle in both electronics and power systems.

Practical Applications & Examples

Electrical circuits form the foundation of modern technology, enabling us to harness electricity to operate a wide range of devices and systems. From smartphones and computers to household appliances and industrial machines, circuits power nearly every aspect of daily life.

For example, a simple battery connected to a light bulb demonstrates how a closed loop allows current to flow, converting electrical energy into light and heat. Safe return paths for current are established through the proper installation of Grounding Electrode Conductors, which helps prevent shock and equipment damage.

Frequently Asked Questions

What is the simplest electrical circuit?

The simplest circuit consists of a power source (such as a battery), a conductor (like a wire), and a load (like a bulb). Closing the loop lets current flow and power the load.

How do series and parallel circuits differ in real life?

Series circuits share a single path, so if one component fails, the entire circuit stops. Parallel circuits have multiple paths, allowing devices to operate independently.

Why is grounding important in electrical circuits?

Grounding provides a safe return path for electricity. It reduces shock hazards and prevents equipment damage during faults or surges.

What role does resistance play in a circuit?

Resistance controls the amount of current flowing. High resistance limits current, while low resistance allows more current to pass.

What is the function of a circuit breaker or fuse?

These protective devices interrupt the current when it becomes too high, preventing overheating, fires, and damage to equipment. To safeguard devices and wiring from excessive currents, engineers rely on Overcurrent Protection Device such as fuses and circuit breakers.

What is an electrical circuit? Why It Matters

Electrical circuits are the backbone of modern technology, powering everything from smartphones and appliances to industrial systems. A firm grasp of fundamental circuit principles is crucial for engineers, electricians, and hobbyists, as it unlocks a deeper understanding of the devices that shape everyday life.

Related Articles

• Electricity Fundamentals

• Electricity Questions

• Electricity History

Electromagnetism is the branch of physics that studies the interaction between electric currents and magnetic fields. It explains how electricity generates magnetism and powers devices such as motors, generators, and transformers in modern electrical systems.

How Should We Define Electromagnetism?

Here's a good way to define electromagnetism: Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles.

✅ Explains the relationship between electricity and magnetism

✅ Governs the operation of motors, generators, and transformers

✅ Forms the basis for electromagnetic waves like light and radio

The electromagnetic force is carried by electromagnetic fields, which are composed of electric fields and magnetic fields, and it is responsible for electromagnetic radiation, such as light.

Who Discovered Electromagnetism?

In 1820, the Danish physicist, Hans Christian Oersted, discovered that the needle of a compass brought near a current-carrying conductor would be deflected. When the current flow stopped, the compass needle returned to its original position. This important discovery demonstrated a relationship between electricity and magnetism that led to the development of the electromagnet and to many of the inventions on which modern industry is based.

Oersted discovered that the magnetic field had no connection with the conductor in which the electrons were flowing, because the conductor was made of nonmagnetic copper. The electrons moving through the wire created the magnetic field around the conductor. Since a magnetic field accompanies a charged particle, the greater the current flow, the greater the magnetic field. Figure 1 illustrates the magnetic field around a current-carrying wire. A series of concentric circles around the conductor represents the field, which, if all the lines were shown, would appear more as a continuous cylinder of such circles around the conductor.

Fig. 1 - Magnetic field formed around a conductor in which current is flowing.

As long as current flows in the conductor, the lines of force remain around it. [Figure 2] If a small current flows through the conductor, there will be a line of force extending out to circle A. If the current flow is increased, the line of force will increase in size to circle B, and a further increase in current will expand it to circle C. As the original line (circle) of force expands from circle A to B, a new line of force will appear at circle A. As the current flow increases, the number of circles of force increases, expanding the outer circles farther from the surface of the current-carrying conductor.

Fig. 2 - Expansion of magnetic field as current increases.

If the current flow is a steady, nonvarying direct current, the magnetic field remains stationary. When the current stops, the magnetic field collapses, and the magnetism around the conductor disappears.

A compass needle is used to demonstrate the direction of the magnetic field around a current-carrying conductor. Figure 3 View A shows a compass needle positioned at right angles to, and approximately one inch from, a current-carrying conductor. If no current were flowing, the north-seeking end of the compass needle would point toward the Earth’s magnetic pole. When current flows, the needle lines itself up at right angles to a radius drawn from the conductor. Since the compass needle is a small magnet, with lines of force extending from south to north inside the metal, it will turn until the direction of these lines agrees with the direction of the lines of force around the conductor. As the compass needle is moved around the conductor, it will maintain itself in a position at right angles to the conductor, indicating that the magnetic field around a current-carrying conductor is circular. As shown in View B of Figure 3, when the direction of current flow through the conductor is reversed, the compass needle points in the opposite direction, indicating that the magnetic field has reversed its direction.

Fig.3 - Magnetic field around a current-carrying conductor.

A method for determining the direction of the lines of force when the direction of current flow is known is illustrated in Figure 4. If the conductor is grasped in the left hand, with the thumb pointing in the direction of current flow, the fingers will be wrapped around the conductor in the same direction as the lines of the magnetic field. This is called the left-hand rule.

Fig.4 - Left-hand rule.

Although it has been stated that the lines of force have direction, this should not be construed to mean that the lines have motion in a circular direction around the conductor. Although the lines of force tend to act in a clockwise or counterclockwise direction, they are not revolving around the conductor.

Since current flows from negative to positive, many illustrations indicate the current direction with a dot symbol on the end of the conductor when the electrons are flowing toward the observer and a plus sign when the current is flowing away from the observer. [Figure 5]

Fig. 5 - Direction of current flow in a conductor.

When a wire is bent into a loop and an electric current flows through it, the left-hand rule remains valid. [Figure 6]

Fig. 6 - Magnetic field around a looped conductor.

If the wire is coiled into two loops, many of the lines of force become large enough to include both loops. Lines of force go through the loops in the same direction, circle around the outside of the two coils, and come in at the opposite end. [Figure 7]

Fig. 7 - Magnetic field around a conductor with two loops.

When a wire contains many such loops, it is referred to as a coil. The lines of force form a pattern through all the loops, causing a high concentration of flux lines through the center of the coil. [Figure 8]

Fig. 8 - Magnetic field of a coil.

In a coil made from loops of a conductor, many of the lines of force are dissipated between the loops of the coil. By placing a soft iron bar inside the coil, the lines of force will be concentrated in the center of the coil, since soft iron has a greater permeability than air. [Figure 9] This combination of an iron core in a coil of wire loops, or turns, is called an electromagnet, since the poles (ends) of the coil possess the characteristics of a bar magnet.

Fig. 9 - Electromagnet.

The addition of the soft iron core does two things for the current-carrying coil. First, the magnetic flux increases, and second, the flux lines become more concentrated.

When direct current flows through the coil, the core becomes magnetized with the same polarity (north and south poles) as the coil would have without the core. If the current is reversed, the polarity will also be reversed.

The polarity of the electromagnet is determined by the left-hand rule in the same manner as the polarity of the coil without the core was determined. If the coil is grasped in the left hand in such a manner that the fingers curve around the coil in the direction of electron flow (minus to plus), the thumb will point in the direction of the north pole. [Figure 10]

Fig. 10 - Left-hand rule applied to a coil.

The strength of the magnetic field of the electromagnet can be increased by either increasing the flow of current or the number of loops in the wire. Doubling the current flow approximately doubles the strength of the field, and similarly, doubling the number of loops approximately doubles the magnetic field strength. Finally, the type of metal in the core is a factor in the field strength of the electromagnet.

A soft iron bar is attracted to either pole of a permanent magnet and, likewise, is attracted by a current-carrying coil. The lines of force extend through the soft iron, magnetizing it by induction and pulling the iron bar toward the coil. If the bar is free to move, it will be drawn into the coil to a position near the center where the field is strongest. [Figure 10-35]

Fig. 11 - Solenoid with iron core.

Electromagnets are utilized in various electrical instruments, including motors, generators, relays, and other devices. Some electromagnetic devices operate on the principle that an iron core, held away from the center of a coil, will be rapidly pulled into its center position when the coil is energized. This principle is utilized in the solenoid, also known as a solenoid switch or relay, where the iron core is spring-loaded off-center and moves to complete a circuit when the coil is energized. 

Related Articles

• Electricity Fundamentals

• Electricity Questions

• Electricity History

What is a voltmeter? A voltmeter is an electrical measuring instrument used to determine voltage across circuit points. Common in electronics, engineering, and power systems, it ensures accuracy, safety, and efficiency when monitoring current and diagnosing electrical performance.

What is a Voltmeter?

A Voltmeter provides a method to accurately measure voltage, which is the difference in electric potential between two points in a circuit, without changing the voltage in that circuit. It is an instrument used for measuring voltage drop.

✅ Ensures accurate voltage measurement for safety and performance

✅ Used in electrical engineering, electronics, and power systems

✅ Helps diagnose faults and maintain efficient operation

Electrical current consists of a flow of charge carriers. Voltage, also known as electromotive force (EMF) or potential difference, manifests as "electrical pressure" that enables current to flow. Given an electric circuit under test with a constant resistance, the current through the circuit varies directly in proportion to the voltage across the circuit. A voltmeter measures potential difference, which directly relates to Ohm’s Law, the fundamental equation connecting voltage, current, and resistance in circuits.

A voltmeter can take many forms, from the classic analog voltmeter with a moving needle to modern instruments like the digital voltmeter (DVM) or the versatile digital multimeter. These tools are essential for measuring electrical values in electronic devices, enabling technicians to measure voltage, current, and resistance with precision and accuracy. While analog units provide quick visual feedback, digital versions deliver more precise measurements across wider voltage ranges, making them indispensable for troubleshooting and maintaining today’s complex electrical systems.

A voltmeter can be tailored to have various full-scale ranges by switching different values of resistance in series with the microammeter, as shown in Fig. 3-6. A voltmeter exhibits high internal resistance because the resistors have large ohmic values. The greater the supply voltage, the larger the internal resistance of the voltmeter because the necessary series resistance increases as the voltage increases. To understand how a voltmeter works, it helps to first review basic electricity, as voltage, current, and resistance form the foundation of all electrical measurements.

Fig 3-6. A simple circuit using a microammeter (tA) to measure DC voltage.

A Voltmeter, whether digital or analog, should have high resistance, and the higher the better. You don't want the meter to draw a lot of current from the power source. (Ideally, it wouldn't draw any current at all.) The power-supply current should go, as much as possible, towards operating whatever circuit or system you want to use, not into getting a meter to tell you the voltage. A voltmeter is commonly used to measure voltage drop across conductors or devices, helping electricians ensure circuits operate efficiently and safely. For quick calculations, a voltage drop calculator provides accurate estimates of conductor losses based on length, size, and current. Understanding the voltage drop formula allows engineers and technicians to apply theoretical principles when designing or troubleshooting electrical systems.

Also, you might not want to keep the voltmeter constantly connected in parallel in the circuit. You may need the voltmeter for testing various circuits. You don't want the behavior of a circuit to be affected the moment you connect or disconnect the voltmeter. The less current a voltmeter draws, the less it affects the behavior of anything that operates from the power supply. Engineers often ask: What is a voltmeter?  They use a voltmeter in power system analysis, where accurate voltage readings are crucial for ensuring safety, reliability, and optimal performance.

Alternative types of voltmeters use electrostatic deflection, rather than electromagnetic deflection, to produce their readings. Remember that electric fields produce forces, just as magnetic fields do. Therefore, a pair of electrically charged plates attracts or repels each other. An electrostatic type utilizes the attractive force between two plates with opposite electric charges or a large potential difference. A voltmeter is used to measure the potential difference. Figure 3-7 portrays the functional mechanics of an electrostatic meter. It constitutes, in effect, a sensitive, calibrated electroscope. A voltmeter draws essentially no current from the power supply. Nothing but air exists between the plates, and air constitutes a nearly perfect electrical insulator. A properly designed electrostatic meter can measure both AC voltage and DC voltage. However, the meter construction tends to be fragile, and mechanical vibration can influence the reading.

Fig 3-7. Functional drawing of an electrostatic voltmeter movement.

It's always good when a voltmeter has a high internal resistance. The reason for this is that you don't want the voltmeter to draw a significant amount of current from the power source. This cur­rent should go, as much as possible, towards working whatever circuit is hooked up to the supply, and not just into getting a reading of the voltage. Additionally, you may not want or need to have the voltmeter constantly connected in the circuit; instead, you might need it for testing various circuits. You don't want the behavior of the circuit to be affected the instant you connect the voltmeter to the supply. The less current a voltmeter draws, the less it will affect the behavior of anything that is working from the power supply.

If you connect an ammeter directly across a source of voltage, a battery, the meter needle will deflect. In fact, a milliammeter needle will probably be "pinned" if you do this with it, and a microammeter might well be wrecked by the force of the needle striking the pin at the top of the scale. For this reason, you should never connect milli-ammeters or micro-ammeters directly across voltage sources. An ammeter, perhaps with a range of 0-10 A, may not deflect to full scale if it is placed across a battery; however, it's still a bad idea to do so, as it will rapidly drain the battery. Some batteries, such as automotive lead-acid cells, can explode under these conditions. This is because all ammeters have low internal resistance. They are designed that way deliberately. They are meant to be connected in series with other parts of a circuit, not right across the power supply. Because voltage is inseparable from current, learning what is current electricity provides deeper insight into why voltmeters are vital diagnostic tools.

But if you place a large resistor in series with an ammeter, and then connect the ammeter across a battery or other type of power supply, you no longer have a short cir­cuit. The ammeter will give an indication that is directly proportional to the voltage of the supply. The smaller the full-scale reading of the ammeter, the larger the resistance needed to get a meaningful indication on the meter. Using a microammeter and a very large resistor in series, it can be devised that draws only a small current from the source.

So, What is a Voltmeter? In summary, a voltmeter is a fundamental instrument for electrical work, allowing professionals and students to accurately measure voltage and understand circuit behaviour. Whether using an analog or digital design, voltmeters and multimeters provide precise insights that support safety, efficiency, and reliable performance in electrical systems.

Related Articles

• Electricity Fundamentals

• Electricity Questions

• Electricity History