Question

The potential difference in volt across the resistance R., in the circuit shown in figure, is $\left(R_1=15\Omega ,R_2=15\Omega ,R_3=30\Omega ,R_4=35\Omega \right)$

• A. 5
• B. 7.5
• C. 15
• D. 12.5

Answer 1

Answer: (C)

Total resistance of the circuit
$R+\frac{\left(R_1+R_2\right)\times R_3}{\left(R_1+R_2\right)+R_3}$
$35+\frac{(15+15)\times 30}{(15+15)+30}$
$=35+\frac{30\times 30}{30+30}=50\Omega$
Current in circuit, $i=\frac{50}{50}=1A$
Current through $R_{3}i=i_2=\frac{1}{2}A$
Potential difference across
$R_3=i\times R_3=\frac{1}{2}\times 30=15V$