## Electrical energy definition

“Electrical energy is produced by moving electric charges commonly through a wire.”When the charge moves from a higher electric potential to a lower potential, it delivers an electric current. Thus, the process, during which charges continuously move from a higher potential to a lower potential, becomes a continuous source of electrical Energy.

## Examples of electrical energy

The turbine runs a generator to produce electrical energy when water falls on it from a higher gravitational potential to a lower gravitational potential. Lightning, electrical charges moving through a wire, batteries in use, electricity stored in capacitors, doorbells, audio speakers, etc.. are few examples.

The unit of electrical energy is the joule (J). It is commonly consumed in very large quantities for the measurement of which joule is a very small unit. Hence, a very large unit of electric energy is needed which is called kilowatt-hour.

### Kilowatt-hour definition

“The amount of energy delivered by the power of one kilowatt in one hour is called kilowatt-hour.”When you pay your electric bill you are charged on the basis of the amount of energy you use, not the power because power companies deal in a huge amount of energy, the most practical unit is the kilowatt-hour, you use a kilowatt-hour of energy when you used one thousand watts of power for one hour. For example, a 100 W light bulb burning for 10 h uses 1KWh of energy.

#### Relation of kWh with MJ:

One kilowatt-hour 1kWh=1000W×1 hour

=1000W×(3600S)

= 3600000J

=3.6MJ

#### Formula to find energy in KWh:

The energy in kilowatt-hour can be obtained by the following formula:

The amount of energy in kWh= watt× times of use in hours/1000

##### Unit followed by an

##### electric meter in our houses:

The electric meter installed in our houses measures the consumption of electric energy in units of kilowatt-hour according to which we pay our electricity bills.

### Calculation of electric bills:

If the cost of one kilowatt-hour i.e one unit is known, we can calculate the amount of electricity bill by the following formula:

Cost of electricity=number of units consumed×cost of one unit

Cost of electricity=watt×times of use in hours/1000 ×cost of one unit

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