# Electric Motor Efficiency: Let's Calculate and Understand the Percentage Efficiency of an Electric Motor!

## What is the useful power out of an electric motor and the total power into the motor?

The useful power out of an electric motor is 20W and the total power into the motor is 80W. What is the percentage efficiency of the motor?

## Calculation and Explanation:

The efficiency of an electric motor can be calculated as the ratio of the output power to the input power, multiplied by 100 to get the percentage.

When it comes to the electric motor in question, we have the following data:

Output Power: 20W

Total Input Power: 80W

To calculate the efficiency, we can use the formula:

**Efficiency = (Output Power / Input Power) * 100**

Substitute the values we have:

**Efficiency = (20W / 80W) * 100 = 25%**

Therefore, the efficiency of this electric motor is 25%, meaning that 25% of the electrical power is converted into useful mechanical energy, while the rest is lost as heat.