Electrical Power Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Electrical Power.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept 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.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Power combines voltage and current — high voltage with high current means rapid energy conversion.

Common stuck point: Power is rate of energy use, not total energy. Energy = power × time.

Sense of Study hint: When solving an electrical power problem, identify which two of the three quantities (voltage, current, resistance) you know. Then choose the matching formula: P = IV if you have both, P = I^2R if you lack voltage, or P = V^2/R if you lack current. Finally, check units — watts = volts × amperes.

Worked Examples

Example 1

easy
A device draws 3 \text{ A} from a 120 \text{ V} outlet. What is the electrical power consumed?

Solution

  1. 1
    Use the electrical power formula: P = VI.
  2. 2
    Substitute the given values: P = 120 \times 3.
  3. 3
    P = 360 \text{ W}

Answer

P = 360 \text{ W}
Electrical power is the rate at which electrical energy is consumed. It can be calculated as voltage times current.

Example 2

medium
A 60 \text{ W} light bulb operates at 120 \text{ V}. What is its resistance and the current it draws?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
An electric kettle rated at 2000 \text{ W} operates for 3 \text{ minutes}. How much energy does it use in kJ?

Example 2

medium
A 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}?
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Background Knowledge

These ideas may be useful before you work through the harder examples.

ohms lawvoltageelectric currentpower