question_answer

In the circuit shown, the value of

A) \[R=15\Omega \]           

B) \[R=30\Omega \]

C) \[E=36V\]

D) \[E=180V\]

Correct Answer: D

Solution :

[d]: Current through \[{{R}_{2}}\]is (2.25 - 1.5) A = 0.75 A. Voltage across \[30\Omega =1.5\times 30=45V\] As \[{{R}_{2}}\]and \[30\Omega \]are in parallel \[\therefore \]Voltage across,\[{{R}_{2}}=45V\] \[\therefore \]\[{{R}_{2}}=\frac{45V}{0.75A}\]\[{{R}_{2}}=60\Omega \] Also,\[{{R}_{1}}=60\Omega \]\[(\because {{R}_{1}}={{R}_{2}}\](Given)) Voltage across, \[{{R}_{1}}=2.25\times 60\Omega =135V\] \[\therefore \]\[E=(135+45)V=180V\]