- Electrical Energy Definition: Electrical energy is the work done by electric charge moving through a potential difference.
- Potential Difference: The potential difference between two points in an electric field is the driving force for the charge movement, measured in volts.
- Electric Current: Electric current is the flow of electric charge through a conductor, measured in amperes.
- Formula for Electrical Energy: Electrical energy is calculated using the formula 𝐸 = 𝑉 × 𝐼 × 𝑡 E=V×I×t.
- Units of Electrical Energy: The basic unit of electrical energy is the joule, with other units like watt-hours and kilowatt-hours used commercially.
What is Electrical Energy?
Electrical energy is the work done when electric charge moves through a potential difference. Start from two points in an electric field.
Take the potential difference between A and B as v volts.
By the definition of potential difference, one coulomb of positive charge travelling from A to B does v joules of work.
If q coulomb moves from A to B, the work is vq joules.
If that q coulomb charge takes t seconds to go from A to B, the rate of work is
Work done per second is power. Then the same term
is electrical power. In differential form, electric power is
The watt is the SI unit of power.
If we place a conductor between A and B, and a charge of q coulombs passes through it, the electric charge passing through a cross-section of the conductor per second is
That quantity is the electric current i in the conductor.
Then
If this current flows through the conductor for a time t, the total work done by the charge is
We define this as electrical energy.
Electrical Energy Definition
Electrical energy is the work done by electric charge. If a constant current i amperes flows through a conductor or other conductive path with potential difference v volts across it, for t seconds, the electric energy is
Electrical Energy Formula
The expression of electric power is
The electrical energy for constant v and i is then For time-varying waveforms, use the integral of instantaneous power. For sinusoidal AC, energy is Vrms times Irms times cos phi times t, where phi is the phase angle between voltage and current.
Unit of Electrical Energy
The SI unit of electrical energy is the joule, equal to one watt-second. Billing uses watt-hours, kilowatt-hours and megawatt-hours. One kilowatt-hour is 3.6 million joules.
Watt Hours
If one watt is used for one hour, the energy used is one watt-hour.
BOT Unit or Board of Trade Unit or Kwh
The usual commercial unit of electrical energy is the kilowatt-hour. One kilowatt-hour is 1000 watt-hours. Supply companies bill electric energy in kilowatt-hours. In older UK and Indian usage that kilowatt-hour is also called the Board of Trade unit, or BOT unit.
