Question

A voltmeter rated as 150V, 20k$\Omega$ when connected in series with a
large resistance R across 110 volt line, the meter reads 5V. Find the
resistance R in $k\Omega$.

Answer 1

Given : $R_1=20000\Omega$ $V=110$ volts

Voltage across $R_1$, $V^{\prime }=5$ volts

Using $V^{\prime }=\frac{R_1}{R_1+R}V$

$\therefore$ $5=\frac{20000}{20000+R}\times 110$ $⟹R=420000\Omega =420$ $k\Omega$