Electric Power

Electric power

Electric power is the rate at which work is done or energy is transformed in an electrical circuit. Simply put, it is a measure of how much energy is used in a span of time. The formula for electric power can be calculated using the relation given below.

\(P\) = \(VI\)


\(P\) is the power \(V\) is the potential difference in the circuit

\(I\) is the electric current

Electric power is measured in watts.

\(1 ~watt\) = \(\frac{1 ~joule}{1~ second}\)

Voltage, current and resistance are related by the following relation

\(V\) = \(IR\)


\(R\) is the resistance in the circuit.

Therefore electric power can also be calculated using the following relations.

\(P\) = \(I^2R\)


\(P\) = \(\frac{V^2}{R}\)

Since power is the rate of energy consumption, energy can directly be calculated using
\(P\) = \(\frac{E}{t}\)


\(E\) is the energy consumption (in Joules)


\(P\) = \(\frac{VQ}{t}\)


\(Q\) is the charge (in Coulombs)

Based on the information given above try the application problem given below:


A 9V battery is connected to a resistor having resistance of 10 Ω. What is the current and power across the resistor?


\(I\) = \(\frac{V}{R}\) = \(\frac{9}{100}\) = \(0.9 ~A\)

\(P\) = \(VI\) = \(9~ ×~ 0.9\) = \(8.1~ J/s\) or \(8.1 ~W\)

Producers and Consumers of Electric Power:

Depending on the function of a component in an electrical circuit, it can be either producers or consumers. A consumer takes in electric energy and transforms it into another type of energy. For example, an electric heater transforms electricity to heat energy. Producers are those that convert some other type of energy to electric energy. For example, in a battery, chemical energy is converted to electricity. Consumers and producers are classified based on whether they consume or produce electric energy.

Stay tuned with byju’s to learn about the types of energy with interesting video lectures.

Practise This Question