Question

In the circuit shown the resistance of voltmeter is 10,000 ohm and that of ammeter reading is 0.10 Amp and voltmeter reading is 12 volt. Then $R$ is equal to

• A. $120\Omega$
• B. $140\Omega$
• C. $116\Omega$
• D. $100\Omega$

Answer 1

The correct option is A $120\Omega$

According to Ohm's law,

$V=IR$

$12=0.1\times R$

$R=\frac{12}{0.1}=120\Omega$

Or

According to KVL

Let, $I$ be the current through the circuit and $r$ be the resistance of voltmeter as

shown in figure.

$(I-i)r=iR$

$\frac{V}{r}r=iR$

$V=iR$

$12=0.1\times R$

$R=\frac{12}{0.1}=120\Omega$