Electricity is the flow of electrons through a conductor, pushed by voltage. Power plants generate it and the grid delivers it to homes.
Basics
Electricity is the flow of electric charge, usually electrons, through a conductor. Voltage pushes the charge, current is the flow (amps), and resistance opposes it (ohms). Ohm’s law: V = I x R.
Generation
Power plants spin turbines with steam, gas, water, wind or use solar panels to make electricity.
Grid
Transformers step up voltage for long-distance transmission (up to 765 kV) and step it down for homes (120 V in the US).
Types
AC (alternating) for the grid, DC for batteries.
Mix in the US
In 2023, natural gas produced about 43 percent, nuclear 19 percent, coal 16 percent, and renewables 21 percent (EIA).
Safety
Never touch downed power lines.
Basics
Electricity is the flow of electric charge, usually electrons moving through a conductor. Three quantities describe it: voltage (the push, measured in volts), current (the flow, measured in amperes) and resistance (opposition to flow, in ohms). Ohm’s law says voltage equals current times resistance. Power in watts is voltage times current. A 100-watt bulb at 120 volts draws about 0.83 amps.
Generation
Most electricity comes from generators that turn a magnet inside coils of wire, a principle discovered by Michael Faraday in 1831. A turbine spins the generator, driven by steam from burning coal, natural gas or nuclear fission, by flowing water, or by wind. Solar panels work differently, converting sunlight directly into electricity through the photovoltaic effect.
The grid
Power plants send electricity through step-up transformers to high-voltage transmission lines at 115,000 to 765,000 volts, since higher voltage reduces energy lost as heat. Substations step the voltage down for distribution lines, and pole transformers lower it to 120/240 volts for homes. In the US, about 5% of electricity is lost in transmission and distribution. The US has three main grids: Eastern, Western and Texas (ERCOT).
Types
- Alternating current (AC) changes direction 60 times a second in the US (60 Hz), and is used for the grid.
- Direct current (DC) flows one way, and is used in batteries, solar panels and electronics.
- Static electricity is a buildup of charge, like a shock from a doorknob.
Mix in the US
In 2023, the US generated about 4.2 trillion kilowatt-hours. Natural gas supplied about 43%, coal about 16%, nuclear about 19%, wind about 10%, hydropower about 6%, solar about 4% and other sources the rest, according to the Energy Information Administration. Renewable sources made up about 21% of the total and are growing fast.
Measuring use
Electricity use is measured in kilowatt-hours (kWh). A typical US home uses about 10,500 kWh a year, or about 29 kWh a day. The average price is about 16 cents per kWh.
Safety
Electricity can kill. Currents of 100 milliamps through the heart can be fatal. Never touch downed power lines, use GFCI outlets near water, do not overload outlets, replace damaged cords, and call a licensed electrician for wiring work.
Voltage, current and units
Electricity is the flow of electrons through a conductor. Voltage (volts) is the push, current (amps) is the flow rate and resistance (ohms) is the opposition, linked by Ohm’s law: V = I x R. Power in watts equals volts times amps. A typical US outlet supplies 120 volts, and a 15 amp circuit can deliver up to 1,800 watts, with 80 percent or 1,440 watts recommended for continuous loads. Electricity usage is billed in kilowatt hours, and the average US home uses about 10,500 kWh per year, according to the Energy Information Administration. In 2023, about 60 percent of US utility scale generation came from fossil fuels, about 19 percent from nuclear, and about 21 percent from renewables. Electric shock can cause burns, cardiac arrest and death, with currents as low as 100 milliamps passing through the chest being potentially fatal. Never touch downed power lines.
Based on data from the US Energy Information Administration and OSHA
