Introduction to Electrical Energy and Power

We need energy to do any work.

Energy is the ability to do work, we use energy every day.

Energy is available in all different forms. In our story, we learn about electrical energy.

Electrical energy is defined as the energy generated by the movement of electrons from one point to another.

It is the energy that's stored in charged particles in the given electric field.

Electric fields are nothing but simply areas surrounding a charged particle.

Let’s understand the concept of electrical energy using a simple circuit.

Here, we have potential connected across a resistor .

Now, according to Ohm’s law, the current flowing through the circuit is given as above,

Electrical potential is the work done to move a unit charge from one point to other point.

The work done to move a charge Q in potential V is given as above,

Again the current is flow of charge per unit time,

Now, The work done is given as above,

The electrical energy is the ability to do work on the charge in the potential .

Let’s use ohm’s law to modify the expression of electrical energy.

According to the Ohm’s law,

Now putting the value of and in the expression, we get,

The S.I. unit of electrical power is Joule and is denoted by .

Now we will see the power associated with the electrical energy.

Power is the rate of work done.

The electrical power is given by,

Power can also be given in the form as above,

Another form of power is as above,

The S.I unit the electrical power is Joule/sec or or watt or .

Let’s look at electrical energy in terms of power.

As power is the rate of work done and work done is the energy,so we can write the energy to be ,

So, The commercial units of electrical energy are watt-hour () or kilowatt-hour ().One kWh is called one unit.

Conversion of the Watt-hour unit to the Joule unit is as above,


Electrical energy is the work done to move a unit charge in a potential.The S.I unit is Joule .

The other expressions for electrical energy are,

Electrical power is the rate of the work done. The S.I. unit is watt or .

Other expressions of electrical power are,

The commercial unit of electrical energy are watt-hour (Wh) and kilowatt-hour (KWh). One kWh is called one unit. One Wh is 3600 J

The End