Power

Power

1. Definition

   • The rate at which energy is transferred, or the rate at which work is done.

2. Note: Energy transfer of 1 joule per second = 1 watt of power

3. Large Powers

   • 1kW = 1 000W (103 W) 1MW = 1 000 000 W (106 W)

4. Formulas

   • Power= energy transferred/time
   • Power= work done/time

5. Units

   • Joules
   • Watts
   • Seconds

6. Examples

   • If a 2,000W kettle boils for 100 seconds, how much energy is used? Energy = Power x Time 2,000 x 100 = 200,000 Joules
   • A PC has a 800W power supply. How long is it used for if it transfers 32,000J of energy? Time = Energy ÷ Power 32,000 ÷ 800 = 40 seconds