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, $i=\frac{50}{50}=1 \,A$
Current through $R_{3} i=i_{2}=\frac{1}{2} \,A$
Potential difference across
$R_{3}=i \times R_{3}=\frac{1}{2} \times 30=15 \,V$