Watthour Meter Explained

Ground electricity underpins grounding and earthing practices, managing earth potential and fault current. It ensures equipotential bonding, surge protection, and safety compliance per IEC/NEC standards for power systems, electronics, and lightning protection.

What Is Ground Electricity?

Ground electricity is the earth reference and return path that stabilizes systems and safely carries fault current.

✅ Provides low-impedance fault current paths to trip protection

✅ Uses earth electrodes, bonding, and grounding conductors

✅ Reduces touch voltage, EMI, and lightning surge damage

Understanding Ground Electricity 

Ground Electricity is a general term that is often used loosely to refer to “Bonding” (Safety Grounding) and “Earth Grounding”.  Personnel of major industries have often misinterpreted grounding to mean that anything in contact with the earth is considered to be grounded. For foundational context, see our overview on how electricity works to understand why grounding concepts are sometimes conflated.

Electrical Grounding is the reference zero for the electrical system.  When we talk about 120 Volts RMS, it represents 120 units above the zero electrical reference.  In residential settings, this reference is commonly tied to service equipment, as explained in our guide to home electricity and typical distribution practices.

Electrical Grounding is the reference zero for the electrical system and all the equipment should be at this same equipment potential plane. Maintaining that equipotential plane is central to electricity safety because it minimizes touch voltage hazards.

According to accident reports, most electrical accidents occur when the earth is used as the safety grounding system (Bonding).   These incidents underscore the broader dangers of electricity when protective paths are improperly designed.

Accident reports details the hazards of using earth as a safety grounding and the practice of electrical grounding the equipment through local grounds. (grounding each individual piece of equipment with a separate ground rod, driven into the earth).  Improper local grounds can also complicate fault clearing during a system electrical fault, increasing damage and downtime.

The best method for ensuring the safety of personnel is to use a “Bonding Conductor”. This conductor should be continuous, with sufficient ampacity and the lowest impedance path back to the circuit interrupting devices, which insures positive operation of the protective devices. A robust bonding network ensures rapid clearing of a ground fault by providing a low-impedance return path for protective devices.

Once a system that connects all the metallic frames of electrical equipment together has been established, then the grounding system must be placed at “Zero Reference Potential”.  The earth grounding electrode should have the lowest resistance value possible, preferably 5 ohms or less.   Coordinating equipment bonding with proper transformer grounding helps maintain stable reference potential across the installation.

This low resistance to earth ground electricity will limit the potential of the electrical system to earth (limiting the stresses placed on components such as switches, insulators and transformers).

It will also reduce the effects of static charges on the electrical system and will protect against lightning strokes, lightning induced voltages, and minimizes the effects of transient over-voltages.

Visit Our Electrical Grounding and Bonding Course 

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An inductive load is common in electrical systems and can significantly impact power quality. Understanding inductive and resistive loads, as well as their impact on the quality of your electricity, is essential for designing and operating an effective electrical system.

What is an Inductive Load?

An inductive load is an electrical device or component that consumes active power while storing energy in a magnetic field due to inductance.

✅ Common in motors, transformers, and relays

✅ Impacts power factor and reactive power demand

✅ Requires compensation with capacitors for efficiency

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In power systems, an inductive load affects the flow of electrical current through conductors, creating conditions that may necessitate careful monitoring. A hot wire and a neutral wire must be properly balanced to avoid hazards, while ground fault circuit interrupters play a vital role in protecting against dangerous faults. Recognizing early signs of a short circuit, such as tripped breakers or overheating, is essential for maintaining system reliability and preventing equipment damage.

How does it affect Power Quality?

Inductive load affects power quality by introducing reactive power into an electrical system. Reactive power is the power that an IL consumes but does not convert into useful work. This can cause a decrease in the overall PF of the system. A low power factor (PF) can result in increased losses, decreased efficiency, and increased power source costs. Additionally, inductive loads can cause voltage drops and fluctuations, which can affect the operation of other electrical devices. Because inductive devices consume reactive power, engineers often use the apparent power formula to calculate their influence on system demand.

What are the types of inductive load?

There are several types of inductive loads, including electric motors, transformers, and heating elements. Electric motors are used in a wide range of applications, from household appliances to industrial machinery. Transformers are used to step up or step down voltage in electrical systems. Heating elements, such as those used in ovens and stovetops, rely on the inductive heating effect to generate heat. One way to minimize the effect of inductive loads on power factor is by installing an automatic power factor controller.

Common examples include:

• Electric motors: ILs are commonly found in electric motors used in various appliances, such as washing machines, refrigerators, and air conditioners. Electric motors require electrical energy to create a magnetic field that rotates the motor's shaft, resulting in a lagging current.

• Transformers are devices used to transfer electrical energy from one circuit to another through electromagnetic induction. They are commonly used in distribution systems to step up or step down the voltage to the required level.

• Fluorescent lights use a ballast to regulate the flow of electricity to the lamp. The ballast contains an IL that helps regulate the electrical current and voltage to the light.

• Welding equipment: Welding equipment, such as arc welders, use ILs to create a strong magnetic field that is used to generate the heat required for welding.

• Induction cooktops: Induction cooktops use magnetic fields to create heat, and this requires the use of ILs to generate the magnetic field.

• Speakers: Speakers use ILs in their voice coils to create a magnetic field that moves the speaker cone and produces sound.

It's essential to understand the different types of electrical load in order to manage consumption and ensure the efficient operation of electrical systems. Different types of loads require different management strategies, and PF correction may be necessary to optimize energy efficiency. Accurate evaluation of an inductive circuit often requires an apparent power calculator to measure kVA, kVAR, and kW contributions.

Frequently Asked Questions

How can you measure the Power Factor of an inductive load?

The PF of an IL can be measured using a PF meter or a digital multimeter. These devices measure the PF by comparing the real power (the power that is actually converted into useful work) to the apparent power (the total power consumed by the load). The PF is then calculated as the ratio of the real power to the apparent power. Inductive devices are often compared with a resistive load, which converts all energy into heat or light without reactive power.

What is the difference between a resistive and an inductive load?

A resistive load is a type of electrical load that converts electrical energy into heat or light, such as an incandescent light bulb or a resistor. A resistive load has a PF of 1, meaning that all of the electricity consumed by the load is converted into useful work. In contrast, an IL stores energy in a magnetic field and has a PF of less than 1. This means that some of the electricity consumed by the load is not converted into useful work.

What are some common examples?

Some common examples of ILs include electric motors, transformers, and fluorescent lights. These loads are found in a wide range of applications, from household appliances to industrial machinery.

How can you reduce the impact of inductive load on a system?

There are several ways to reduce the impact of ILs on an electrical system. One way is to improve the PF of the system by adding PF correction capacitors. These capacitors can help offset the reactive electricity consumed by ILs, thereby increasing the PF of the system. Another approach is to utilize soft starters or variable frequency drives with electric motors, which can reduce inrush current and minimize voltage fluctuations. Finally, using a high-efficiency supply or reducing the number of ILs in a system can also help reduce the impact of ILs on PQ. To balance inductive and capacitive elements, engineers apply power factor correction techniques that restore efficiency and reduce system losses.

By understanding the different types, measuring the PF, and reducing its impact on a system, electrical engineers can design and operate systems that are more efficient, reliable, and cost-effective.

It's worth noting that they are not the only types of electrical loads that can impact PQ. Capacitive loads, such as capacitors and fluorescent lights, can also introduce reactive power into a system. Additionally, purely resistive loads, such as resistors and incandescent light bulbs, do not introduce reactive power but can still affect PQ in other ways, including the generation of heat.

Understanding the different types of electrical loads and their impact on PQ is essential for designing and operating efficient and reliable electrical systems. While they can introduce reactive power and affect PF, there are ways to minimize their impact and improve PQ. By taking a holistic approach to electrical system design and operation, engineers can create systems that meet the needs of their users while minimizing costs and maximizing efficiency. Since inductive loads influence reactive currents, using the reactive power formula helps quantify their effect on power system design and operation.

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A watthour meter measures electrical energy consumption in kilowatt-hours (kWh) for residential, commercial, and industrial applications, ensuring accurate billing, energy management, and compliance with utility standards.

What is a Watthour Meter?

✅ Measures total electrical energy in kilowatt-hours (kWh) over time

✅ Supports accurate billing, energy monitoring, and demand analysis

✅ Used in residential, commercial, and industrial revenue metering

Advancements in Watthour Meter Technology and Energy Measurement

Watthour meter technology plays a crucial role in modern electrical engineering and maintenance by providing accurate measurement and monitoring of energy consumption. These devices are indispensable for managing energy efficiency, optimizing power distribution, and ensuring compliance with regulatory standards. For electrical professionals, understanding how they operate and are maintained is essential to minimize energy losses and enhance the reliability of electrical systems. With the growing demand for precise energy data in both residential and industrial applications, staying informed about advancements in watthour meter technology is more important than ever. Understanding how a watthour is calculated helps clarify how a watthour meter tracks total energy usage for accurate billing. 

Your electric utility is not too interested in how much power you're consuming for one ap­pliance or even how much power a single household is drawing at any given time. By far the greater concern is the total energy that is used over a day, a week, a month or a year. Electrical energy is measured in watt-hours or, more commonly for utility pur­poses, in kilowatt-hours (kWh). The device that measures this consumption is the watt-hour meter or kilowatt-hour meter. For a deeper understanding of the units used in metering, see our guide on electrical energy and how it is measured in kilowatt-hours.

The most common method for measuring electrical energy is by using a small elec­tric motor device, whose speed depends on the current, and thereby on the power at a constant voltage. The number of turns of the motor shaft, in a given length of time, is di­rectly proportional to the number of watt hours consumed. The motor is placed at the point where the utility wires enter the house, apartment or building. This is usually at a point where the voltage is 234 V. This is split into some circuits with 234 V, for heavy-duty appliances such as the oven, washer and dryer, and the general household circuits for lamps, clock radios and television sets. The principles behind watthour meters are closely tied to basic electricity and the relationship between active power and time.

Understanding the Spinning Disk in Electromechanical Watthour Meters

You've surely seen the little disk in the utility meter going around and around, sometimes fast, other times slowly. Its speed depends on the power you're using. The total number of turns of this little disk, every month, determines the size of the bill you will get, as a function also, of course, of the cost per kilowatt hour for electricity.

Kilo-watt-hour meters count the number of disk turns by means of geared, rotary drums or pointers. The drum-type meter gives a direct digital readout. The pointer type has several scales calibrated from 0 to 9 in circles, some going clockwise and others go­ing counterclockwise. Mechanical and electronic meters both rely on the concepts of electrical resistance and current to provide precise readings.

How to Read a Pointer-Type Watthour Meter Accurately

Reading a pointer-type utility meter is a little tricky because you must think in whatever direction (clockwise or counterclockwise) the scale goes. An example of a pointer-type utility meter is shown in Fig. 3-11. Read from left to right. For each little meter, take down the number that the pointer has most recently passed. Write down the rest as you go. The meter in the figure reads 3875 kWh. If you want to be really pre­cise, you can say it reads 3875-1/2 kWh. To place watt hour metering in historical context, explore our history of electricity page and learn how early meters evolved into today’s advanced devices.

Fig. 3-11 An example of a utility kilo-watthour meter. The reading is a little more than 3875 kWh.

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Generate electricity via power generation methods: generators, turbines, photovoltaics, fuel cells, and microgrids; optimized by inverters, AC/DC conversion, smart grid control, energy storage, high-efficiency transmission, and reliable distribution networks integration.

What Is Generate Electricity?

Generate electricity converts energy to electric power using generators, turbines, and inverters for grid supply.

✅ Electromechanical conversion with synchronous or induction generators

✅ Power electronics: rectifiers, inverters, MPPT, AC/DC conversion

✅ Sources: PV, wind, hydro, gas turbines; grid-tied or microgrid

There are several ways to generate electricity. There are "thermal" methods like coal, oil, natural gas, peat, biomass - in all these cases, the energy that is trapped in the form of carbon (found in the ground in the form of fossil fuels) is released by heating the carbon. The problem, as we all know too well, is that the breakdown of carbon through burning it is the by product of gases such as carbon dioxide, a main contributor to global warming. But that is not all. When we burn carbon, there are other pollutants that are released into the atmosphere like sulphur dioxide and nitrous oxide. These chemicals are the principal contributors to acid rain. For a broader overview of these processes, see how electricity generation works across different fuel types.

We also produce electricity by non-fossil fuel methods by using uranium in nuclear fission "reactors" to create enough heat to boil water, which in turn produces large quantities of high pressure steam. This steam turns a turbine which turns a generator that manufactuers electic power through the conversion of mechanical energy into electrical energy. This sequence illustrates how electricity is generated from thermal sources in practice.

There is more than one renewable source of energy to generate electricity, by using solar panels to convert sunlight and wind energy to convert kinetic energy into electric power. In any case dependable power generation, transmission and distribution is critical for providing heat, light and power for human activities. Electric power has been generated for the purpose of powering human technologies for at least 120 years from various sources of potential energy. The first power plants were run on wood, while today we rely mainly on oil, natural gas, coal, hydroelectric and nuclear power and a small amount from hydrogen, solar energy, tidal harnesses, wind generators, and geothermal sources. Many utilities are expanding portfolios with alternative electricity options to meet emissions targets.

Methods To Produce Electric Power

Understanding the landscape of sources of electricity helps frame the methods described below.

Rotating turbines attached to electrical generators produce most commercially available electricity. Turbines may be driven by using steam, water, wind or other fluids as an intermediate energy carrier. The most common usage is by steam in fossil fuel power plants or nuclear power plants, and by water in hydroelectric dams. Alternately, turbines can be driven directly by the combustion of natural gas or oil. Combined cycle gas turbine plants offer efficiencies of up to 60%. They generate power by burning natural gas in a gas turbine and use residual heat to generate additional electric power from steam. Wind turbines create power by using the wind. Solar updraft towers use wind that is artificially produced inside the chimney by heating it with sunlight. Solar parabolic troughs and solar power towers concentrate sunlight to heat a heat transfer fluid that is used to produce steam to turn a turbine. In all these configurations, the core electricity generator converts rotational energy into electrical output.

Within wind applications, the modern electricity windmill integrates power electronics and control systems to maximize capacity factor.

Small power generators are often powered by reciprocating engines burning diesel, biogas or natural gas. Diesel engines are often used to create power, usually at low voltages. Biogas is often combusted where it is produced, such as a landfill or wastewater treatment plant, with a reciprocating engine or a microturbine, which is a small gas turbine. These distributed assets play a growing role in overall electricity production for remote sites and microgrids.

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Wireless electricity transmits power without wires using electromagnetic fields, such as magnetic resonance or microwave transmission. It enables charging devices remotely, powering sensors, and improving efficiency in smart grids, EVs, and wireless charging systems.

What is Wireless Electricity?

Wireless electricity refers to the transmission of electrical energy without physical conductors like wires.

✅ Powers devices through electromagnetic fields, like inductive coupling

✅ Enables contactless charging in consumer electronics and EVs

✅ Supports smart grids, IoT, and remote sensors with flexible energy delivery

Wireless electricity, also known as wireless power transmission, was first conceptualized by Nikola Tesla, a pioneer in the field of alternating current (AC) electricity. Tesla’s groundbreaking experiments at Colorado Springs in 1899 showcased how power could be transmitted without wires using a magnetic field. He used a Tesla coil to transmit 100 million volts of high power over a distance of 26 miles, wirelessly powering 200 light bulbs and an electric motor. His vision was to develop a wireless system capable of transmitting power over long distances with minimal energy loss.

Tesla’s system relied on a high-frequency alternating current and magnetic resonance to transmit power wirelessly. His experiments with the Tesla coil laid the groundwork for modern wireless technologies, including short-range wi

reless power transmission systems, such as wireless charging pads and Wi-Fi routers. Wireless charging pads today utilize magnetic fields to transmit power to devices, a concept similar to Tesla’s idea of harnessing the Earth’s resonance to transmit power over longer distances. Tesla’s vision extended beyond short-range wireless systems—he dreamed of a global system where energy flows freely through the air without requiring a direct line of sight.

Tesla’s experiments also demonstrated the efficiency of wireless systems. The Tesla coil could transmit power wirelessly to fluorescent light bulbs even when they were several feet away from the coil. This concept of powering devices wirelessly has evolved over time, with companies like Wi-Charge developing systems to transmit power wirelessly to small devices. In Tesla’s time, he envisioned a world where any amount of power could be transmitted wirelessly across the globe. However, financial struggles eventually led to the abandonment of his wireless power transmission projects, including the unfinished Wardenclyffe tower on Long Island. Devices powered wirelessly still rely on efficient energy flow, making concepts such as electrical resistance and impedance crucial to design and performance.

Despite Tesla’s challenges, modern advancements have kept his vision alive. Short-range wireless power transmission systems, like those used in Wi-Fi routers and wireless charging pads, are now commonplace. These technologies utilize magnetic fields to transmit power wirelessly over short distances, offering a practical solution for wirelessly charging devices such as smartphones and laptops. Wi-Charge is exploring the potential of wirelessly charging devices without requiring close contact, enabling more flexible and efficient energy distribution. Tesla’s coil and modern systems like Wi-Charge operate based on resonant principles, closely related to inductance and capacitance.

Modern Innovations in Wireless Electricity

Recent breakthroughs have brought Tesla’s dream closer to reality:

• In 2024, DARPA successfully transmitted 800 watts of power over 5 miles using a laser beam—enough to make popcorn at the receiver site.

• KAIST in South Korea demonstrated the ability to charge 40 smartphones at once using magnetic resonance over a distance of 5 meters.

• Detroit’s Corktown district now hosts a functioning inductive charging roadway, allowing EVs to charge wirelessly while in motion.

These examples show that wireless electricity is no longer a distant vision but a rapidly advancing technology with real-world applications. Concepts such as watts, volts, and amperes remain fundamental even in advanced wireless systems.

Types of Wireless Power Transmission Technologies

Applications of Wireless Electricity

• Consumer Electronics: Wireless charging pads and smart home devices are now common.

• Electric Vehicles (EVs): Inductive charging roads and parking pads reduce dependency on cable stations.

• Medical Implants: Enables powering of implants and biosensors without invasive wiring.

• Remote Sensors: In agriculture, factories, and infrastructure, wireless power extends sensor life.

• Smart Grids: Flexible energy distribution for remote locations and emergency response.

Challenges and Future Outlook

Despite its promise, wireless electricity faces challenges:

• Efficiency drops over distance

• Alignment issues in inductive systems

• Line-of-sight limitations in laser and IR systems

• Safety regulations for high-power beaming

However, the future is promising. Emerging materials, such as metamaterials and metasurfaces, are enhancing transmission efficiency. AI-enhanced beam control, dynamic alignment systems, and frequency-agnostic receivers are under development.

From Tesla's early experiments to DARPA's record-setting laser transmission, wireless electricity is evolving into a transformative force. As the technology matures, its applications will expand, powering a world that may one day be truly wire-free.

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Green electricity integrates renewable energy sources such as solar PV, wind turbines, and hydropower into smart grids, improving power quality, decarbonization, efficiency, and reliability for industrial loads and utility-scale networks.

What is green electricity?

Green electricity is renewable-source power via smart grids to cut emissions and enhance system efficiency.

✅ Integrates PV, wind, hydro with power electronics and converters

✅ Enhances grid stability via inverters, FACTS, and smart protection

✅ Reduces CO2, improves efficiency, supports microgrids and storage

Green electricity is a term describing what is thought to be environmentally friendly sources of electricity. Typically, this refers to renewable and non-polluting energy power sources. For a broader perspective on how different technologies contribute, see this overview of sources of electricity across modern grids.

Green electricity includes natural energetic processes which can be harnessed with little pollution. Anaerobic digestion, geothermal power, wind power, small-scale hydropower, solar power, biomass power, tidal power and wave power fall under such a category. Some versions may also include power derived from the incineration of waste. Comparisons with other clean options are summarized in this guide to alternative electricity solutions used worldwide.

Energies Wind Electricity 
The winds that blow across the UK can be harnessed by turbines to provide Green electricity. Wind turbines sited in suitable locations already provide a small, but growing percentage of the UK's electricity, and are used successfully all around the world. In fact wind power is the world's fastest growing energy source! Wind turbine technology has greatly improved over the last ten years, making wind turbines quieter and more efficient so that electricity generated from the wind is now often competitive with traditional coal-fired and nuclear power stations. Wind turbines are also beginning to be built at sea — in the future much of our electricity could come from these offshore windfarms. Understanding how turbines integrate into national systems is covered in this primer on electricity generation methods and planning.

Solar Electricity
Many people believe that we don't get much solar Green electricity here in the UK. In fact solar power is already being used to provide essential power for many types of equipment being used in both remote and urban areas across the country. A solar photovoltaic (PV) module works by converting sunlight directly into electricity (even on cloudy days) using semiconductor technology. The vast majority of solar modules available today use "waste" silicon from the computer chip industry as the semiconductor material. They can be integrated into buildings and even made into roof tiles virtually indistinguishable from normal tiles. 
Solar Electricity can also be used to heat water directly using specially designed collectors. Even in winter a useful amount of hot water can be produced from roof top collectors. A third way to use solar energy is simply to design buildings to make maximum use of the sun. Using this so-called 'passive solar' approach, much of the energy that we currently use for heating, lighting and air conditioning can be saved. Homeowners can explore practical steps to generate electricity with rooftop PV and storage.

Hydro Electricity
Water turbines have been used to provide Green electricity for over 100 years and presently provide over 1% of the UK's electricity. Although most of the possible sites for large hydropower stations in the UK have already been developed, there is a large potential for smaller schemes. These can either use a small dam or work as a 'run of the river' system which has a minimal impact on the local environment. Design considerations for small schemes are outlined in this resource on water electricity systems for communities.

Wave Electricity
Many different devices have been designed over the years to try and capture some of this huge energy resource — the latest one has recently started generating Green electricity on the isle of Islay, off the West Coast of Scotland. In this machine waves hitting the shore are channelled into a large tube to power a specially designed turbine. With the proper support, wave power could provide a significant proportion of the UK's electricity needs in the future.

Tidal Electricity
Tidal power has been used in Britain for over a thousand years — at the time of the Doomsday book over 5,000 tide powered mills were recorded. Unlike other Green electricity renewable energy sources, which depend on the weather, tidal power is as predictable as the tides themselves. One way to capture tidal energy is to build a barrage across an estuary, storing water behind it as the tide rises and then releasing the stored water through turbines at low tide. Several sites around the UK could be suitable for this type of tidal system, the largest being the Severn Estuary. Another way is to use 'marine current turbines', which work like underwater wind turbines, harnessing tidal currents instead of the winds.

Geothermal Electricity
Geothermal energy comes from hot rocks deep underground. In some parts of the world steam comes to the surface and can be used to run steam turbines to produce Green electricity directly. In other places water can be pumped down and heated by the rocks to make steam. Geothermal energy can also be used to provide hot water and heating for buildings. Case studies of enhanced systems are available in this overview of geothermal electricity projects worldwide.

Biomass Electricity
Either agricultural wastes or specially grown plants can be used as a fuel to run small Green electricity power stations. As plants grow they absorb carbon dioxide (the main gas responsible for climate change) which is then released when the plants are burnt. So using biomass does not add any extra carbon dioxide into the atmosphere. Specially grown 'energy crops' provide not only an environmentally sound source of electricity, but also an important new opportunity for farmers. Analyses of supply chains and grid impacts appear in this review of electricity production from biomass and other renewables.

Landfill gas Converted to Electricity
As rubbish decomposes in the landfill sites where our household waste is dumped, it gives off methane gas. This gas can be captured and burnt in a gas turbine to produce an attractive Green electricity tariff. Burning the gas does give off carbon dioxide but since methane, which is emitted from the landfill site, is in fact a much more powerful greenhouse gas it is better to burn it than to allow the methane to escape into the atmosphere. There are already many landfill gas systems operating in the UK.

Waste Incineration Electricity
The UK generates an enormous amount of waste, and space at landfill sites is quickly running out. The best solution would be to recycle as much of the waste as possible, but instead incinerators are being constructed to burn the waste. In some cases the energy is being used to generate green electricity. However many environmentalists are still concerned about the emission of harmful dioxins and also about the loss of a valuable resources that could have been recycled. You can read about Greenpeace's views on incineration.

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