Electrical Resistance Explained


Electrical Resistance

Electrical resistance is the opposition to the flow of electric current in a material. It is measured in ohms (Ω) and depends on the conductor’s length, thickness, material, and temperature.

 

What is Electrical Resistance?

Electrical resistance is a fundamental concept in engineering that defines how much a material opposes the flow of electric current. Measured in ohms (Ω), resistance (Ω) plays a crucial role in circuit design, power distribution, and electronic applications.

✅ Measured in ohms (Ω) and calculated using Ohm’s Law

✅ Influenced by material, length, area, and temperature

✅ Key factor in circuit safety, design, and energy loss

 

Think of electricity moving like water through a pipe. If the pipe is narrow or obstructed, less water flows through it. Similarly, in a wire or conductor, certain materials make it harder for electrons to move freely. This obstruction results in energy loss, often seen as heat.

The ease or difficulty of electric charge movement depends on the conductivity of a material. Metals like copper allow current to flow easily, while rubber or glass inhibit it entirely. This behavior plays a key role in how systems are designed and protected. Discover how resistors are used in circuits to manage voltage and protect components by providing controlled resistance.

 

Electrical Resistance – Example Values by Material/Component

Material/Component Approx. Resistance Notes
Copper wire (1 meter, 1mm²) ~0.017 ohms Very low resistance, ideal for conductors
Aluminum wire (1m, 1mm²) ~0.028 ohms Higher resistance than copper
Iron wire (1m, 1mm²) ~0.10 ohms Often used in heating elements
Nichrome wire (1m, 1mm²) ~1.10 ohms High-resistance alloy used in toasters and heaters
Human body (dry skin) 1,000–100,000 ohms Varies greatly with moisture and contact
Incandescent light bulb ~240 ohms (cold) Resistance increases when hot
Resistor (carbon film) Fixed (e.g., 220 ohms) Used to control current in circuits
Air (dry) ~1 trillion ohms (insulator) Excellent natural insulator unless ionized
Superconductor 0 ohms Only at extremely low temperatures (near absolute zero)

 

Electrical Resistance Definition

Several factors affecting electrical resistance include the type of material, temperature, and the dimensions of the conductor. When an electric charge moves through a material, its ease of flow depends on the material’s conductivity. A high-conductivity material allows charges to move more freely, resulting in lower resistance. The resistance of a conductor increases with its length and decreases with its cross-sectional area. Therefore, the resistance of a wire is directly related to both its physical properties and the material from which it is made. The resistance of a conductor depends heavily on its length and cross-sectional area, as outlined in our resistance formula breakdown.

This opposing property is quantified using Ohm’s Law:

R = V / I

Where:

  • R is the resistive value in ohms

  • V is voltage (volts)

  • I is current (amperes)

Another useful expression involves material properties:

R = ρ × (L / A)

Where:

  • ρ is resistivity (material-specific)

  • L is length

  • A is cross-sectional area

These formulas show that the longer or thinner the conductor, the harder it is for current to move through it.

 

Unit of Electrical Resistance – The Ohm (Ω)

The ohm is the SI unit of resistance, named after German physicist Georg Ohm. One ohm is defined as the resistance between two points of a conductor when a potential difference of one volt causes a current of one ampere to flow.

Common multiples:

  • kΩ (kilo-ohm) = 1,000 ohms

  • MΩ (mega-ohm) = 1,000,000 ohms

Resistance can be measured using a multimeter, and is especially important in designing and troubleshooting power  and electronic circuits. To understand how voltage and resistance interact in a circuit, see our guide on Ohm’s Law.

 

Ohm’s Law and Circuit Function

Ohm’s Law helps us understand how voltage, current, and resistance relate. For example:

  • Increase the resistive load, and current drops.

  • Increase voltage with fixed resistance, and current rises.

These principles help control energy flow, prevent overloads, and design efficient systems.

 

Measuring and Expressing Opposition

The ohm (Ω) is the standard unit used to quantify this phenomenon. One ohm means that a current of one ampere flows when one volt is applied. Components with fixed values, like resistors, are labelled accordingly—e.g., 100 Ω, 1 kΩ, or 1 MΩ.

To measure the current-limiting capacity of a material, a digital multimeter is used. It applies a small voltage and calculates the resulting current flow to determine the opposition level. If you're working with different wire types, explore the unit of electrical resistance for conversion insights and resistance ranges.

 

Real-World Examples of Resistance

  • Heating Elements: Toasters, ovens, and electric heaters utilize high-resistance materials, such as nichrome wire.

  • Power Transmission: Long-distance wires are designed with low resistance to reduce energy loss as heat.

  • Electronic Components: Resistors regulate current in circuits, protecting components from overload.

For real-world scenarios involving current flow, our article on voltage drop explains how resistance affects electrical efficiency over distance.

 

Factors Affecting Electrical Resistance

  • The resistance of a conductor depends on:

    • Material – copper vs. aluminum vs. nichrome

    • Length – longer wires restrict current more

    • Thickness – wider wires allow easier flow

    • Temperature – many materials resist current more when heated

    Thus, the resistance of a wire can vary dramatically depending on where and how it’s used. Materials with high conductivity (like silver or copper) allow electrons to move with minimal restriction, whereas poor conductors like rubber greatly hinder charge movement.

 

Superconductors – Zero Resistance?

In some materials, when cooled to extremely low temperatures, resistance drops to zero. These superconductors enable electricity to flow without energy loss, but their use is limited to specialized fields, such as MRI machines or experimental power lines, due to cost and cooling requirements.

 

Frequently Asked Questions

 

What causes electrical resistance?

It results from collisions between electrons and atoms in a conductor, which convert energy into heat.

 

What is the formula for calculating it?

 R = V/I or R = ρ × (L / A)

 

How is it measured?

With a multimeter in ohms (Ω), using a small test voltage and measuring current. Learn how instruments like a digital multimeter are used to measure opposition to current flow in electrical systems.

 

Why is this concept important?

It controls current flow, prevents damage, and enables functions like heating or dimming.

 

Can resistance ever be zero?

Yes—in superconductors under specific extreme conditions.

Electrical resistance is a foundational concept in understanding how electricity behaves in materials and systems. From household wiring to high-voltage power lines and sensitive electronics, it plays a crucial role in determining safety, efficiency, and performance. For a broader view on electric flow and material response, read about electrical conductivity and current electricity.

 

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Electricity Generation Power Production

Electricity generation is the process of producing electric power from various energy sources, including fossil fuels, solar, wind, hydro, and nuclear. It uses turbines and generators to convert mechanical or thermal energy into electrical energy for residential, commercial, and industrial use.

 

What is Electricity Generation?

Electricity generation is a process that involves producing electrical power from various sources.

✅ Converts mechanical, thermal, or chemical energy into electrical power

✅ Uses generators powered by steam, wind, water, or combustion

✅ Essential for powering homes, industries, and transportation

 

In the United States, power production from utility-scale generators was about 4.1 trillion kilowatt-hours (kWh) in 2019. Fossil fuels, including coal, natural gas, and petroleum, produced about 63% of the electricity, while nuclear energy produced around 20%. The remaining 17% was generated from renewable energy sources, including solar photovoltaics, wind turbines, and hydroelectric power production. To explore the full process from fuel to flow, see our detailed guide on how electricity is generated.

 

Electricity Generation Sources Compared

Energy Source How It Generates Electricity Global Usage (approx.) Carbon Emissions Renewable?
Coal Burns to heat water → steam → turbine spins generator 35% High No
Natural Gas Combusts to drive turbines directly or via steam 23% Moderate No
Nuclear Nuclear fission heats water → steam → turbine 10% Low No (but low-carbon)
Hydropower Flowing water spins turbines 15% Very Low Yes
Wind Wind turns large blades connected to a generator 7% Zero Yes
Solar PV Converts sunlight directly into electricity via photovoltaic cells 5% Zero Yes
Geothermal Uses Earth’s internal heat to create steam and turn turbines <1% Very Low Yes
Biomass Burns organic material to generate heat for steam turbines ~1.5% Moderate (depends on fuel) Partially

 

Hydroelectric Power Generation

Hydroelectric power production units utilize flowing water to spin a turbine connected to a generator. Falling water systems accumulate water in reservoirs created by dams, which then release it through conduits to apply pressure against the turbine blades, driving the generator. In a run-of-the-river system, the force of the river current applies pressure to the turbine blades to produce power. In 2000, hydroelectric generation accounted for the fourth-largest share (7 percent) of electricity production, at 273 billion kWh. Explore how water and electricity interact in hydroelectric plants, where falling water is converted into renewable energy.

 

Non-Hydro Renewable Energy Sources in Electricity Generation

Non-water renewable sources, including geothermal, refuse, waste heat, waste steam, solar thermal power plants, wind, and wood, contribute only small amounts (about 2 percent) to total power production. In 2019, power production from these sources totalled 84 billion kWh. The entire electric power industry production in 2019 was 3,800 billion kWh, with utilities' net production accounting for 3,015 billion kWh and net generation by non-utility power producers 785 billion kWh.

 

U.S. Electricity Generation by Energy Source: Trends and Shifts

The United States' share of electrical energy production from different sources has changed more rapidly since 2007 than ever since 1950. On the other hand, Canada's energy production is significantly less than that of the USA, primarily in Ontario and British Columbia. At least three trends are catalyzing these changes: (1) the low price of natural gas; (2) the rise in renewable and distributed generation due to falling costs; and (3) recent Federal and State policies impacting production. There are many innovative ways to generate electricity, from traditional fossil fuels to cutting-edge renewable technologies.

 

Fuel Source Diversity in U.S. and Canadian Electricity Production

Diversity is a key attribute in U.S. and Canadian electricity production. However, rather than being the result of a deliberative, long-term national initiative, this diversity has developed through spurts of growth in specific production technologies at different times. This is often due to policies, historical events, capital costs, fuel costs, and technological advancements.

 

Historical Growth of Electricity Generation by Energy Source

Most energy sources have experienced eras of significant capacity growth in terms of terawatt hours: hydro (1930‒1950, not shown); coal (1950-1985); nuclear (1960‒1980); natural gas (1990‒2010); and renewables (2005‒present). Nuclear energy is increasingly recognized as a key solution for achieving carbon reduction goals—learn how it contributes to net-zero emissions.

 

Changing U.S. Power Generation Mix: Centralized to Distributed Energy

The U.S. generation mix has undergone significant changes over the past few decades and is projected to continue evolving substantially. The U.S. generation fleet is transitioning from one dominated by centralized generators with high inertia and dispatchability to one more hybridized, relying on a mixture of traditional, centralized production and variable utility-scale and distributed renewable energy production.

 

Power Generation Technologies: From Diesel Engines to Wind Turbines

To generate power, various sources are utilized, including diesel engines, gas turbines, and nuclear power plants. Fossil fuels, including natural gas and coal, are burned to create hot gases that go through turbines, which spin the copper armature inside the generator and generate an electric current. In a nuclear power plant, nuclear reactions generate heat that is used to heat water, which then turns into steam and passes through a turbine to produce electricity. In a wind turbine, the wind pushes against the turbine blades, causing the rotor to spin and generating an electric current. In a hydroelectric turbine, flowing or falling water pushes against the turbine blades, causing the rotor to spin and generating an electric current. As the global energy landscape evolves, many experts are re-evaluating the role of nuclear power—learn more in our feature on the future of nuclear energy.

 

Electricity Generation by Utilities and Non-Utility Power Producers

To meet these immediate demands, utilities and nonutility power producers operate several electric generating units powered by various fuel sources. Renewable fuels, such as water, geothermal, wind, and other renewable energy sources like solar photovoltaics, are used as sources of power, alongside fossil fuels and uranium.

 

motor

 

diagram

 

Fossil Fuel Electricity Generation: Coal, Natural Gas, and Petroleum

Coal was the fuel used to generate the largest share (51.8 percent) of electricity in 2000, with natural gas and petroleum accounting for 16.1 percent and 3 percent, respectively. Steam-electric generating units burn fossil fuels, such as coal, natural gas, and petroleum, to produce steam. This steam is then used to turn a turbine into a generator, producing power. On the other hand, gas turbine generators burn fuels to create hot gases, which also go through a turbine, spinning the copper armature inside the generator and generating an electric current. Diesel engine generators are also used, where the combustion occurs inside the engine's cylinders, which are connected to the generator's shaft. The mechanical energy provided by the turbine drives the generator, which in turn produces energy.

 

Electricity Generation Trends and the Global Shift Toward Renewables

The production of electrical energy has experienced various eras of significant capacity growth in the United States, Canada, and other countries worldwide. The future of power production is transitioning to a more hybridized generation fleet that relies on a combination of traditional, centralized power production and variable utility-scale and distributed renewable energy sources. Low natural gas prices drive this transition, the rise of renewable and distributed energy sources, and recent Federal and State policies that impact generation. Discover the most common renewable energy sources powering the shift toward a cleaner, more sustainable electricity future.

 

Enhance your expertise in clean energy with our comprehensive Renewable Energy Grid Integration Training course. Designed for electrical professionals, this course covers the challenges and solutions associated with connecting solar, wind, and other renewable energy sources to the power grid. Stay ahead of industry trends, improve system reliability, and gain valuable skills to support the transition to a sustainable energy future. Enroll today and take the next step in your professional development.

 

Frequently Asked Questions

How is electricity generated from renewable energy sources?

Electricity is generated from renewable energy sources by converting the energy of the sun, wind, water, or earth into electrical energy. For example, solar photovoltaic panels generate power directly from sunlight, wind turbines to generate electricity from wind energy, and hydroelectric power plants generate power from falling water.


What are the different types of fossil fuels used?

The different types of fossil fuels used include coal, natural gas, and petroleum. Coal is the most commonly used fossil fuel for energy production, followed by natural gas and oil.


What are the advantages and disadvantages of using nuclear power plants for electricity generation?

Advantages of using nuclear power plants include that they produce a large amount of energy with a low amount of fuel, emit less carbon dioxide than fossil fuel power plants, and are not dependent on weather conditions like wind or solar power. Disadvantages include the risks associated with nuclear accidents, the high cost of building and maintaining nuclear power plants, and the long-term storage of nuclear waste.


How do gas turbines work to generate electricity?

Gas turbines burn natural gas or other fuels to heat air, which expands and drives the turbine. Finally, the turbine is connected to a generator that converts the mechanical energy of the turbine into electrical energy.


What is the role of steam turbines in electricity generation?

Steam turbines are commonly used to convert thermal energy from steam into mechanical energy that drives a generator. Steam is produced by burning fossil fuels or using heat from nuclear reactions or geothermal sources. The steam drives the turbine blades, which are connected to the generator to produce electricity.


What are some examples of non-renewable energy sources?

Examples of non-renewable energy sources used for power production include fossil fuels, such as coal, natural gas, and petroleum, as well as nuclear energy.


How is electricity generated and distributed in the United States?

Various power plants, including those powered by fossil fuels, nuclear energy, and renewable energy sources, generate electricity in the United States. Electric power is transported over a complex network of power lines and transformers to homes, businesses, and other consumers through local utility companies. The Federal Energy Regulatory Commission (FERC) and various state regulatory agencies regulate power distribution.

 

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Capacitance Explained

Capacitance: Understanding the Ability to Store Electricity

Capacitance is an essential concept in electrical circuits, and it describes the ability of a capacitor to store electrical energy. Capacitors are electronic components used in many circuits to perform various functions, such as filtering, timing, and power conversion. Capacitance is a measure of a capacitor's ability to store electrical energy, and it plays a crucial role in the design and operation of electrical circuits. This article provides an overview of capacitance, including its definition, SI unit, and the difference between capacitor and capacitance.

 

What is Capacitance?

Capacitance is the ability of a capacitor to store electrical charge. A capacitor consists of two conductive plates separated by a dielectric material. The conductive plates are connected to an electrical circuit, and the dielectric material is placed between them to prevent direct contact. When a voltage source is applied to the plates, electrical charge builds up on the surface of the plates. The amount of charge that a capacitor can store is determined by its capacitance, which depends on the size and distance between the plates, as well as the dielectric constant of the material.

The energy storing capability of a capacitor is based on its capacitance. This means that a capacitor with a higher capacitance can store more energy than a capacitor with a lower capacitance. The energy stored in a capacitor is given by the formula:

Energy (Joules) = 0.5 x Capacitance (Farads) x Voltage^2

The ability to store energy is essential for many applications, including filtering, timing, and power conversion. Capacitors are commonly used in DC circuits to smooth out voltage fluctuations and prevent noise. They are also used in AC circuits to filter out high-frequency signals.

 

What is Capacitance and the SI Unit of Capacitance?

Capacitance is defined as the ratio of the electrical charge stored on a capacitor to the voltage applied to it. The SI unit of capacitance is the Farad (F), which is defined as the amount of capacitance that stores one coulomb of electrical charge when a voltage of one volt is applied. One Farad is a relatively large unit of capacitance, and most capacitors have values that are much smaller. Therefore, capacitors are often measured in microfarads (µF) or picofarads (pF).

The capacitance of a capacitor depends on several factors, including the distance between the plates, the surface area of the plates, and the dielectric constant of the material between the plates. The dielectric constant is a measure of the ability of the material to store electrical energy, and it affects the capacitance of the capacitor. The higher the dielectric constant of the material, the higher the capacitance of the capacitor.

 

What is the Difference Between Capacitor and Capacitance?

Capacitor and capacitance are related concepts but are not the same thing. Capacitance is the ability of a capacitor to store electrical energy, while a capacitor is an electronic component that stores electrical charge. A capacitor consists of two conductive plates separated by a dielectric material, and it is designed to store electrical charge. Capacitance is a property of a capacitor, and it determines the amount of electrical charge that the capacitor can store. Capacitance is measured in Farads, while the capacitor is measured in units of capacitance, such as microfarads (µF) or picofarads (pF).

 

What is an Example of Capacitance?

One example of capacitance is a common electronic component known as an electrolytic capacitor. These capacitors are used in a wide range of electronic circuits to store electrical energy, filter out noise, and regulate voltage. They consist of two conductive plates separated by a dielectric material, which is usually an electrolyte. The electrolyte allows for a high capacitance, which means that these capacitors can store a large amount of electrical energy.

Another example of capacitance is the human body. Although the capacitance of the human body is relatively small, it can still store a significant amount of electrical charge. This is why people can sometimes feel a shock when they touch a grounded object, such as a metal doorknob or a handrail. The capacitance of the human body is affected by several factors, including the size and shape of the body, as well as the material and proximity of the objects it comes into contact with.

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Voltage Drop Formula

The voltage drop formula is V = I × R, where V represents the voltage drop, I represents the current in amperes, and R represents the resistance in ohms. It calculates the amount of voltage lost through a conductor and is essential for designing safe and efficient electrical systems.

 

What is Voltage Drop Formula?

A voltage drop formula can help you manually calculate the voltage drop in cables under full load in branch circuits. It does not matter if you are working with copper or aluminum conductors. To accurately calculate the voltage drop for a given cable size, length, and current, you need to know the resistance of the type of cable you’re using. 

✅ V = I × R for DC circuits

✅ Accounts for impedance in AC circuits

✅ Helps ensure safe, efficient electrical design

Use our voltage drop calculator to quickly determine wire size, conductor efficiency, and line loss for safer, more reliable electrical installations.

 

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To determine voltage drop in an electrical system, engineers and electricians use a standard formula that accounts for conductor resistance, current, and circuit length. The National Electrical Code (NEC) provides guidelines for the maximum voltage drop allowed in various installations to ensure efficiency and safety. For both single-phase and three-phase circuits, excessive voltage drop can lead to poor equipment performance and energy loss. To simplify calculations, a voltage drop calculator can quickly assess whether a circuit meets NEC recommendations and optimize conductor sizing accordingly. You can learn more about how electrical resistance affects circuits in our detailed voltage drop guide, which explains causes, calculations, and solutions for safe, efficient power distribution.

 

DC / single phase calculation

The voltage drop V in volts (V) is equal to the wire current I in amps (A) times 2 times one way wire size length L in feet (ft) times the wire resistance per 1000 feet R in ohms (Ω/kft) divided by 1000:

 

Vdrop (V) = Iwire (A) × Rwire(Ω)

Iwire (A) × (2 × L(ft) × Rwire(Ω/kft) / 1000(ft/kft))

 

The voltage drop V in volts (V) is equal to the wire current I in amps (A) times 2 times one way wire length L in meters (m) times the wire resistance per 1000 meters R in ohms (Ω/km) divided by 1000:

 

Vdrop (V) = Iwire (A) × Rwire(Ω)

Iwire (A) × (2 × L(m) × Rwire (Ω/km) / 1000(m/km))

 

3 phase calculation

The line-to-line voltage drop V in volts (V) is equal to the square root of 3 times the wire current I in amps (A) times one-way wire length L in feet (ft) times the wire resistance per 1000 feet R in ohms (Ω/kft) divided by 1000:

 

Vdrop (V) = √3 × Iwire (A) × Rwire (Ω)

= 1.732 × Iwire (A) × (L(ft) × Rwire (Ω/kft) / 1000(ft/kft))

 

The line-to-line voltage drop V in volts (V) is equal to the square root of 3 times the wire current I in amps (A) times one-way wire length L in meters (m) times the wire resistance per 1000 meters R in ohms (Ω/km) divided by 1000:

 

Vdrop (V) = √3 × Iwire (A) × Rwire (Ω)

= 1.732 × Iwire (A) × (L(m) × Rwire (Ω/km) / 1000(m/km))

 

Wire diameter calculations

The n gauge wire diameter, dn in inches (in), is equal to 0.005in times 92 raised to the power of 36 minus gauge number n, divided by 39:

 

dn (in) = 0.005 in × 92(36-n)/39

 

The n gauge wire diameter dn in millimetres (mm) is equal to 0.127mm times 92 raised to the power of 36 minus gauge number n, divided by 39:

 

dn (mm) = 0.127 mm × 92(36-n)/39

 

Wire cross-sectional area calculations

The n gauge wire's cross-sectional area An in kilo-circular mils (kcmil) is equal to 1000 times the square wire diameter d in inches (in):

 

An (kcmil) = 1000×dn2 = 0.025 in2 × 92(36-n)/19.5

 

The n gauge wire's cross-sectional area An in square inches (in2), is equal to pi divided by 4 times the square wire diameter d in inches (in):

 

An (in2) = (π/4)×dn2 = 0.000019635 in2 × 92(36-n)/19.5

 

The n gauge wire's cross-sectional area, An, in square millimetres (mm2), is equal to pi divided by 4 times the square wire diameter d in millimetres (mm):

 

An (mm2) = (π/4)×dn2 = 0.012668 mm2 × 92(36-n)/19.5

 

Wire resistance calculations

The n gauge wire resistance R in ohms per kilofeet (Ω/kft) is equal to 0.3048×1000000000 times the wire's resistivity ρ in ohm-meters (Ω·m) divided by 25.42 times the cross-sectional area An in square inches (in2):

 

R(Ω/kft) = 0.3048 × 109 × ρ(Ω·m) / (25.42 × An (in2))

 

The n gauge wire resistance R in ohms per kilometre (Ω/km) is equal to 1000000000 times the wire's resistivity ρ in ohm-meters (Ω·m) divided by the cross-sectional area An in square millimetres (mm2):

 

R(Ω/km) = 109 × ρ(Ω·m) / An (mm2)

 

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Electricity Generator

Electricity generator converts mechanical energy to electrical power via electromagnetic induction using a prime mover, alternator, stator, and rotor, delivering regulated AC/DC output, high efficiency, and stable voltage and frequency.

 

What Is an Electricity Generator?

An electricity generator converts mechanical energy to electric power using electromagnetic induction, AC or DC.

✅ Converts rotational torque into regulated AC or DC output

✅ Uses stator, rotor, and excitation for voltage regulation

✅ Applied in power plants, gensets, microgrids, and renewables

 

An Electricity Generator can create electricity by converting mechanical energy into electrical current that can be used in electrical systems. Wind turbines house such generators to convert the kinetic energy of wind into power that can feed power grids. involve the production of electrons that are a part of every atom,. Electricity is what results when electrons are flowing through a conductor. Ultimately, all that is needed to generate electricity is a metal wire for a conductor and a catalyst to start the electrically charged electrons flowing. You see, unlike natural gas and other fossil fuels that are mined from the Earth, electricity is a manufactured product. Most generators operated by electric utilties are alternating current (ac) generators but there are still some direct current (dc) generators in existence. For a clear primer on charge, current, and how generators relate to these basics, see what is electricity to ground these concepts.

Alternating current is easily generated by means of a rotating magnet windings in a coil of wire, or by a rotating coil of wire inside a powerful magnet. In either case, the ac appears between the ends of the length of wire. This takes place in an electricity generator, which was invented by Michael Faraday. A portable generator can be used as backup power during a power outage. If you want a step-by-step view of induction and circuit behavior, consult how electricity works for context beyond this overview.

The ac voltage that a generator (motor) can develop depends on the strength of the magnets field, the number of turns in the wire coil, and the speed at which the magnet or coil rotates. The ac frequency depends only on the speed of rotation. Normally, for utility ac, this speed is 3,600 revolutions per minute (rpm), or 60 complete revolutions per second (rps), so that the frequency is 60 Hz. Design choices that set coil turns, flux, and rotational speed are discussed in how electricity is generated with practical examples.

When a load, such as a light bulb or heater, is connected to an ac generator, it becomes more difficult to turn the generator. The more power needed from a generator, the greater the amount of power required to drive it. This is why it is not possible to connect a generator to, for instance, your stationary bicycle, and pedal an entire city into electrification. There's no way to get something for nothing. The electrical power that comes out of a generator can never be more than the mechanical power driving it. In fact, there is always some energy lost, mainly as heat in the generator. Your legs might generate 50 W of power to run a small radio, but nowhere near enough to provide electricity for a household. Realistic scenarios for human power and small prime movers are outlined in generate electricity to help size expectations.

The efficiency of a generator is the ratio of the magnet generate power output to the driving power, both measured in the same units (such as watts or kilowatts), multiplied by 100 to get a percentage. No generator is 100 percent efficient. But a good one can come fairly close to this ideal. Typical loss mechanisms and efficiency ranges across technologies are compared in electricity generation for further reading.

At power plants, the power generators can be huge. Each one can be as big as a house. In a power plant, each electricity generator is driven by a massive turbine. Often, steam drives the turbine, and the steam is obtained via heat derived from natural energy source, like falling water. Capacity factors, fuel choices, and turbine types are covered in electricity production to illustrate real-world plant operation.

There are many different sources of electricity and many different ways electricity can be produced and consumed. For instance, modern wind turbines are explained in electricity windmill with details on siting, capacity, and grid integration.

 

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Voltage Drop Explained

Voltage drop occurs when electrical voltage decreases as current flows through a conductor. It can cause poor equipment performance, energy loss, and overheating. Discover how selecting the proper wire size and material can help minimize voltage drop in electrical systems.

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What is Voltage Drop?

Voltage drop (VD) is a common issue in electrical systems where the voltage (V) at the end of a circuit is lower than at the beginning due to resistance in the wiring.

✅ A decrease in V along a wire or circuit due to resistance or impedance

✅ Leads to reduced equipment performance and higher energy consumption

✅ Prevented by proper wire sizing, shorter runs, and low-resistance materials

 

Voltage Drop Definition

Voltage drop can lead to inefficient equipment operation or even failure. Solving electrical potential drop involves ensuring proper wire sizing, minimizing long-distance wiring runs, and using materials with lower resistance. Calculating the voltage drop for specific circuits and adjusting the installation accordingly helps maintain optimal performance and prevent power loss.

Any length or size of wires will have some resistance, and running a current through this dc resistance will cause the voltage to drop. As the length of the cable increases, so does its resistance and reactance increase in proportion. Hence, circuit V drop is particularly a problem with long cable runs, for example, in larger buildings or on larger properties such as farms. This technique is often used when properly sizing conductors in any single-phase, line-to-line electrical circuit. This can be measured with a voltage drop calculator.

Electrical cables have a carrying capacity of current that always presents inherent resistance, or impedance, to the flow of current. Voltage drop is measured as the amount of loss which occurs through all or part of a circuit due to what is called cable "impedance" in volts.

Too much resistance in wires, otherwise known as " excessive voltage drop ", in a cable's cross-sectional area can cause lights to flicker or burn dimly, heaters to heat poorly, and motors to run hotter than normal and burn out. This condition causes the load to work harder with less energy, pushing the current.

 

Voltage Drop per 100 Feet of Copper Wire (Single Phase, 60 Hz, 75°C, 120V Circuit)

(Values are approximate, in volts, for a 2% limit)

Wire Size (AWG) Max Current (Amps) Max Distance (Feet) Voltage Drop (at max distance)
14 15 50 2.4 V
12 20 60 2.4 V
10 30 80 2.4 V
8 40 100 2.4 V
6 55 130 2.4 V
4 70 160 2.4 V
2 95 200 2.4 V
1/0 125 250 2.4 V

 

Key Takeaways

  • Larger wires (lower AWG numbers) carry more current with less VD.

  • Longer distances require thicker wires to stay within VD limits.

  • A 2% VD is often used as a conservative design target in electrical systems.

 

How is this solved?

To decrease the voltage drop in a circuit, you need to increase the size (cross-section) of your conductors – this is done to lower the overall resistance of the cable length. Certainly, larger copper or aluminum cable sizes increase the cost, so it’s essential to calculate the voltage drop and determine the optimum wire size that will reduce voltage drop to safe levels while remaining cost-effective.

 

How do you calculate voltage drop?

Voltage drop refers to the loss of electricity that occurs when current flows through a resistance. The greater the resistance, the greater the voltage drop. To check the voltage drop, use a voltmeter connected between the points where the voltage drop is to be measured. In DC circuits and AC resistive circuits, the total of all the voltage drops across series-connected loads should add up to the V applied to the circuit (Figure 1).


 

Fig. 1. Measuring voltage drops across loads

Read our companion article Voltage Drop Calculator. For more information, see our article: Voltage Drop Formula.

Each load device must receive its rated power to operate properly. If not enough is available, the device will not operate as it should. You should always be certain that the V you are going to measure does not exceed the range of the voltmeter. This may be difficult if the V is unknown. If such is the case, you should always start with the highest range. Attempting to measure a V higher than the voltmeter can handle may cause damage to the voltmeter. At times you may be required to measure a V from a specific point in the circuit to ground or a common reference point (Figure 8-15). To do this, first connect the black common test probe of the voltmeter to the circuit ground or common. Then connect the red test probe to whatever point in the circuit you want to measure.

To accurately calculate the drop for a given cable size, length, and current, you need to accurately know the resistance of the type of cable you’re using. However, AS3000 outlines a simplified method that can be used.

The table below is taken from AS3000 electrical code, which specifies ‘Amps per %Vd‘ (amps per percentage VD) for each cable size.  To calculate the dop for a circuit as a percentage, multiply the current (amps) by the cable length (metres); then divide this Ohm number by the value in the table.

For example, a 30m run of 6 mm² cable carrying 3-phase 32A will result in a 1.5% drop: 32A × 30m = 960A / 615 = 1.5%.

Learn more about real-world voltage drop issues on our Voltage Dropping in Power Quality page.

 

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Voltage Drop Calculator

A voltage drop calculator helps electricians and engineers estimate line loss, wire size, and circuit efficiency. By inputting conductor length, current, and material, it ensures proper electrical design, safe voltage regulation, and compliance with power distribution standards.

 

What is a Voltage Drop Calculator?

A voltage drop calculator (VDC) is crucial for any electrical engineer or designer. It enables them to calculate VD accurately, which is essential for maintaining an efficient and safe electrical system.

✅ Quickly estimates voltage loss in electrical circuits

✅ Helps select the correct wire size for load and distance

✅ Supports NEC code compliance and system efficiency

 

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Voltage drop calculators are used in various applications, including residential, commercial, and industrial settings, and offer several benefits, such as accurate calculations, time savings, cost reduction, and hazard prevention. Additionally, engineers can ensure the electrical system operates efficiently and safely by considering factors such as cable sizing, wire gauge, and the type of conductor used. Want the full math? Visit our voltage drop formula guide for detailed equations and examples.

There are numerous VDCs available on the internet, and one of the best places to find them is on Google Play.


Applications of Voltage Drop Calculators

VDCs are used in various residential, commercial, and industrial applications. For instance, in residential applications, VDCs help determine the appropriate wire size for the electrical service panel, the length of wires, and the type of installation, ensuring that the electrical system operates correctly and safely. Additionally, VD formulas can be used to calculate resistance and reactance in both single-phase and three-phase electrical systems. It is measured in feet over a specified length.

In commercial applications, voltage drop calculators are used to design and maintain electrical systems in buildings such as hospitals, schools, and offices. These buildings require careful design to ensure that they meet the power requirements of the building and are safe for occupants. VDCs play a crucial role in this process by calculating the VD in the circuit and determining the appropriate wire size and other specifications.

In industrial applications, VDCs are used to design and maintain electrical systems in factories and other industrial settings. These systems require careful design to ensure they meet the equipment's power requirements and are safe for workers. VDCs determine the circuit's VD, the appropriate wire size, and other specifications to ensure that the electrical system operates efficiently and safely. For an overview of the general principles of voltage drop across AC and DC systems, read our article.

 

Benefits of Using a VDC

Using a VDC offers several benefits, including:

Accurate Calculations: VDCs use complex algorithms to calculate VD accurately. This ensures that the electrical system operates efficiently and safely.

Saves Time: VDCs save time by automating the process of calculating VD. This allows engineers to focus on other aspects of the design process, such as equipment selection and installation.

Reduces Costs: By accurately calculating VD, engineers can select the appropriate wire size and other specifications, thereby reducing the cost of the electrical system.

Prevents Hazards: Accurate calculation of VD prevents electrical hazards, including fires and shocks. 

 

FREE Voltage Drop Calculator 

 

Cable Sizing and Wire Gauge

One of the most critical factors to consider when designing an electrical system is cable sizing and wire gauge. The conductor's or wire gauge's size is critical in determining the amount of current that can flow through the conductor without causing excessive VD or overheating. American Wire Gauge (AWG) is the standard system used to specify wire sizes, providing a range of conductor sizes based on the wire's cross-sectional area. Additionally, the National Electrical Code (NEC) provides guidelines for ampacity and voltage drop (VD) for various conductor sizes and types of installations.

 

Copper or Aluminum Conductors

The type of conductor used in an electrical system also affects the voltage drop (VD). Copper and aluminum conductors are the most commonly used materials, with copper being preferred due to its lower resistance and higher conductivity. However, aluminum conductors are less expensive and commonly used in larger conductors and power transmission lines.

 

Frequently Asked Questions


How do I calculate voltage drop?

To calculate VD, you can use the VD formula, which is V = IR, where V is the voltage drop, I is the current flowing through the conductor, and R is the resistance of the conductor. By knowing the current, resistance, and length of the conductor, you can calculate the VD and determine whether it falls within acceptable limits.


How do I use it?

To use a VDC, you need to input the current flowing through the conductor, the length of the conductor, and the wire gauge or cable size. The tool then uses complex algorithms to calculate the VD in the circuit accurately. Based on the results, you can determine the appropriate wire size, cable length, and other specifications necessary to maintain an efficient and safe electrical system.


How is voltage drop calculated in a circuit?

VD is calculated in a circuit using Ohm's Law, which states that the VD across a conductor is equal to the product of the current and resistance. By knowing the current, resistance, and length of the conductor, you can calculate the VD and determine whether it falls within acceptable limits.


What factors affect voltage drop in a circuit?

The factors that affect VD in a circuit include the current flowing through the conductor, the length of the conductor, the resistance of the conductor, and the wire gauge or cable size. Other factors, such as the type of conductor and installation, can also affect VD.


Why is it important to calculate voltage drop?

Calculating VD is essential in maintaining an efficient and safe electrical system. VD can impact the performance of electrical equipment and devices, leading to hazards such as fires and electrical shock. By accurately calculating VD, engineers can select the appropriate wire size, cable length, and other necessary specifications to maintain an efficient and safe electrical system.


What are the benefits of using a VDC?

Using a VDC offers several benefits, including accurate calculations, time savings, cost reduction, and hazard prevention. By accurately calculating VD, engineers can select the appropriate wire size and other specifications, thereby reducing the cost of the electrical system. In addition, calculating VD accurately can prevent electrical hazards such as fires and shocks.


Are there any limitations to using a VDC?

While VDCs offer numerous benefits, they also have some limitations. For example, they rely on the accuracy of the input parameters, but may overlook other factors that can affect voltage drop, such as temperature and ambient conditions. Additionally, they may not be suitable for complex electrical systems.


What is the voltage drop per 100 ft?

The VD per 100 ft depends on various factors, including the current flowing through the conductor, the conductor's length, its resistance, and the wire gauge or cable size. Therefore, it is essential to calculate the VD accurately to determine the appropriate wire size and cable length necessary to maintain an efficient and safe electrical system.


What is a rule of thumb for voltage drop?

The rule of thumb for VD is that the VD in a circuit should not exceed 3% for power circuits and 5% for lighting circuits. These values are based on the National Electrical Code (NEC) guidelines, ensuring the electrical system operates efficiently and safely.

Southwire Voltage Drop Calculator

 

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