# Electric Power

In physics, an electric power measure of the rate of electrical energy transfer by an electric circuit per unit time. Denoted by P and measured using the SI unit of power is the watt or one joule per second. Electric power is commonly supplied by sources such as electric batteries and produced by electric generators.

## Electric Power Definition

Electric power is the rate at which work is done or energy is transformed into an electrical circuit. Simply put, it is a measure of how much energy is used in a span of time.

 Symbol P SI Unit Watt, joule per second Scalar or Vector Scalar Quantity Formula P=VI

## Electric Power Formula

The formula for electric power is given by

 P = VI

where,

P is the power

V is the potential difference in the circuit

I is the electric current

Power can also be written as

 P = I2R P = V2/ R

The above two expressions are got by using Ohms law, Where, Voltage, current, and resistance are related by the following relation

V = IR
Where,

• R is the resistance in the circuit.
• V is the potential difference in the circuit
• I is the electric current

### Power Energy Formula

Since power is the rate of energy consumption, energy can directly be calculated using

 $P=\frac{E}{t}$

Where,

E is the energy consumption (in Joules)

t is the time in seconds

 $P=\frac{VQ}{t}$

Where,

• Q is the charge (in Coulombs)
• V is Potential difference in volts
• t is the time in seconds

## Electric Power Problems

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

Example:

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

Solution:

I = V/R = 9/100 = 0.9 A

P = VI = 9 × 0.9 = 8.1 J/s or 8.1 W

## Frequently Asked Questions – FAQs

### Define electric Power

Electric power measure of the rate of electrical energy transfer by an electric circuit per unit time.

### Write the SI unit of electric power

The SI unit of electric power is the watt.

### Write the electric power formula and explain the terms

The electric power is given by P = VI. Where V is the potential difference, I is the electric current and P is the electric power.

### Is electric power a scalar quantity or vector quantity?

Electric power is the scalar quantity.

### How can we express power using Ohms law?

Power formula can be rewritten using Ohms law as P =I^2R or P = V^2/R. Where V is the potential difference, I is the electric current, R is the resistance and P is the electric power

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