KinexiaLEARN PHYSICS

Electric Potential — Battery Voltage (Worked Example)

Easy
Problem

A battery does 18 J of work pushing 1.5 C of charge from one terminal to the other. What is the battery's voltage?

Given

  • W = 18 J

  • q = 1.5 C

Find

The potential difference V.

Principle

Voltage is energy per unit charge: V = W/q — the definition of the volt.

Formula

Solution

  1. Write the definition: V=W/qV = W/q

  2. Substitute: V=18/1.5V = 18/1.5

  3. Divide: V=12 VV = 12\ \mathrm{V}

12 V

Unit check

J ÷ C = V — correct by definition.

What this means physically

12 V — a car-battery-style voltage: each coulomb of charge carries 12 J of energy around the circuit.

Common mistake

Confusing energy with voltage. The 18 J is total energy; voltage is energy per coulomb — divide by the charge.