Question

Two resistors $ 400\,\Omega $ and $ 800\,\Omega $ are connected in series with a 6V battery. The potential difference measured by voltmeter of $ 10\,\Omega $ across $ 400\,\Omega $ resistor is

• A. 2V
• B. 1.95V
• C. 3.8V
• D. 4V

Answer 1

Answer: (B)

Here, the resistances of $ 400\,\Omega $ and $ 10000\,\Omega $
are in parallel, their effective resistance
$ {{R}_{P}} $ will be $ {{R}_{P}}=\frac{400\times 10000}{400+10000} $
$=\frac{5000}{13}\Omega $
Total resistance of the circuit,
$=\frac{5000}{13}+800=\frac{15400}{13}\Omega $
Current in the circuit
$ I=\frac{6}{15400/13}=\frac{39}{7700}A $
Potential difference across voltmeter
$=I{{R}_{p}}=\frac{39}{7700}\times \frac{5000}{13}=1.95\,V $