# PHYS 2212 Module 5.5

## Electrical Energy and Power 5.5 Electrical Energy and Power

### Learning Objectives

By the end of this section, you will be able to:

• Express electrical power in terms of the voltage and the current
• Describe the power dissipated by a resistor in an electric circuit
• Calculate the energy efficiency and cost effectiveness of appliances and equipment

### Electrical Power in Circuits

In physics 1, you discussed mechanical power which is the rate at which mechanical work is done: .

The units for power are J/s, which are called Watts, symbol: W (but don’t confuse the unit W with the symbol for work, they’re not the same thing). Generally, power is the measure of how quickly energy is transferred into or out of a system.

Here we will discuss electrical power, which is also measured in J/s = W (watts). But instead of looking at how the kinetic energy or the gravitational potential energy changes, we will focus on how the electric potential energy changes in time. Practice!