Electric Field — Parallel-Plate Capacitor (Worked Example)

Given

• V = 12 V

• d = 2.0 mm = 0.0020 m

Find

The field E.

Principle

Between parallel plates the field is uniform: E = V/d — voltage divided by separation.

Formula

Solution

1. Convert: $d = 0.0020\ \mathrm{m}$

2. Substitute: $E = 12/0.0020$

3. Divide: $E = 6000\ \mathrm{V/m}$

Unit check

V ÷ m = V/m = N/C — correct.

What this means physically

6000 V/m — strong enough to steer electron beams in old oscilloscopes. Halving the plate gap would double the field at the same voltage.