Question

The voltmeter shown in figure, reads 18 V across the $50\Omega$ resistor. Find the resistance of the voltmeter.

Answer 1

The voltage across the 24 ohms resistor is $30-18=12$ v

The current flowing is $12v/24\Omega =0.5$ A

The current through the 50 Ω resistor is $18v/50\Omega =0.36$ A

So the current through the voltmeter is $0.5A-0.36A=0.14$ A

The resistance of the voltmeter is $18v/0.14A=128.6\Omega$