Practice Electrical Power in Physics
Use these practice problems to test your method after reviewing the concept explanation and worked examples.
Quick Recap
The rate at which electrical energy is converted to other forms of energy (heat, light, motion). Measured in watts (W).
Power tells you how quickly a device uses energy — a 100 W bulb converts energy twice as fast as a 50 W bulb.
Example 1
easyA device draws 3 \text{ A} from a 120 \text{ V} outlet. What is the electrical power consumed?
Example 2
mediumA 60 \text{ W} light bulb operates at 120 \text{ V}. What is its resistance and the current it draws?
Example 3
mediumAn electric kettle rated at 2000 \text{ W} operates for 3 \text{ minutes}. How much energy does it use in kJ?
Example 4
mediumA kettle is rated at 2000 \text{ W} and operates on a 250 \text{ V} supply. (a) What current does it draw? (b) What is its resistance? (c) How much energy does it use in 3 \text{ minutes}?