question_answer

In the circuit shown, the current through the \[4\Omega \]resistor is 1 A when the points P and M are connected to a DC voltage source. The potential difference between the points M and N is

A) 1.5V  

B)                                        1.0 V

C) 0.5 V                     

D)        3.2 V

Correct Answer: D

Solution :

Key Idea: In parallel resistances, potential difference across them is same. Potential difference across PM \[V=4\times 1=4\] volt (ie, across \[4\,\Omega \]) Equivalent resistance of lower side arm, \[{{\operatorname{R}}_{eq}}=1+\frac{0.5\times 0.5}{0.5+0.5}=1.25\Omega \] Now the circuit can be shown as Let current I flows in lower branch, so \[1.25I=4V\]or\[I=\frac{4}{1.25}=3.2A\] Therefore, 3.2 A current flows in \[1\Omega \] resistance, hence potential difference between M and N is \[V'=3.2\times 1=3.2\] volt