Question

In the circuit given $E=6.0V,R_1=100\Omega ,R_2=R_3=50\Omega$, $R_4=75\Omega$. The equivalent resistance of the circuit, in ohms, is

• A. 11.875
• B. 26.31
• C. 118.75
• D. None of these

Answer 1

Answer: (C)

In given circuit three resistance $R_2,R_4$ and $R_3$ are parallel.

$\frac{1}{R}=\frac{1}{R_2}+\frac{1}{R_4}+\frac{1}{R_3}$
$=\frac{1}{50}+\frac{1}{50}+\frac{1}{75}$
$=\frac{75+75+50}{50\times 75}$
$R=\frac{50\times 75}{75+75+50}$
$=\frac{50\times 75}{200}=\frac{75}{4}\Omega$
$=18.75\Omega$
This resistance is in series with $R_1$.
$\therefore R_{\text{resultant }}=R_1+R=100+18.75$
$=118.75\Omega$