Question

A charge of `12 C` is passing through points A and B on a circuit. If the charge's electric potential changes from `36 J` to `18 J`, what is the voltage between points A and B?

Answer 1

`1.5 \text{V}`

Explanation:

Voltage is defined as the electric potential difference between two points per unit charge. So, find the electric potential difference between points `A` and `B` as experienced by `12` units of charge, then divide by `12` to find per charge.

`\frac{E_A - E_B}{12} = \frac{36 \text{J}-18 \text{J}}{12 \text{C}} = \frac{18\text{J}}{12 \text{C}} = \frac{3}{2} \text{V} = 1.5 \text{V}`

Note that volts is joules per coulomb, so the units here make physical sense (checking that the units make sense is a useful way to troubleshoot maths in physics).