Knowledge you can walk. Read the idea below, then step up to the general, across to peers or down to the specific.
Physical
Electrical Energy
Electrical energy is the energy moved from place to place when electric charges flow across a voltage.
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The idea
Electrical energy is the energy transferred by moving electric charges. Charges move between two points when the points have different electric potential, a gap called a potential difference or voltage. As the charges cross that gap, work is done and the energy of some system changes. The energy in joules equals the charge that moved, in coulombs, multiplied by the voltage it crossed, in volts.
Power companies usually sell electrical energy by the kilowatt-hour. A kilowatt-hour is the power in kilowatts multiplied by the running time in hours, and it equals 3.6 million joules. An electricity meter keeps a running total of the energy delivered to each customer.
Electrical energy is useful because it is easy to turn into other forms. An electric heater turns it into thermal energy. Current flows through the heating element, and the charges hand their energy to it, so the element gets hotter. In the same way, motors turn electrical energy into motion and lamps turn it into light.
Check yourself
Question 1 of 2
How many joules are in one kilowatt-hour?
Composition
what it's made of
- Electric charge — The moving particles, usually electrons in a wire, that carry the energy.
- Potential difference — The gap in electric potential, or voltage, that charges move across.
- Electric current — The flow of charge through a conductor such as a copper wire.
- Energy transfer — As charges lose potential, they pass energy to something else, such as a heater element.
- Kilowatt-hour — The everyday unit used to measure and sell electrical energy.
Connection
how it relates
Under Energy Forms
Change
how and why it evolves
- Past
- People first used electricity mainly for lighting and the telegraph, and later it spread into homes and factories.
- Now
- Today utilities track each customer's use with an electricity meter and bill it by the kilowatt-hour.
- Next
- More electrical energy is likely to come from wind and solar power, and more cars and home heating systems may run on it.