In a voltmeter showing 120 V, the current is 15 mA. Determine the resistance of the voltmeter.

Given:

U = 120 Volts – voltage of the electrical circuit to which the voltmeter is connected;

I = 15 mA – current in the electrical circuit.

It is required to determine R (Ohm) – the resistance of the voltmeter.

Let’s convert the units of measurement of current strength from milliamperes to amperes:

I = 15 mA = 15 * 10-3 = 0.015 Ampere.

To determine the resistance of a voltmeter, you must use the following formula:

U = I * R, from here we find:

R = U / I = 120 / 0.015 = 8000 Ohm (8 kOhm).

Answer: the resistance of the voltmeter is 8000 Ohm (8 kOhm).