Question
In the circuit shown, the current through the 4 Ω resistor is 1 A when the points P and M are connected to a DC voltage source. The potential difference between the point M and N is 
-
1.5 V
-
1.0 V
-
0.5 V
-
3.2 V
Solution
D.
3.2 V
In parallel resistances, the potential difference across them is same.
Potential difference across PM
V = 4 x 1 = 4 Volt (ie, across 4 Ω)
Equivalent resistance of lower side arm, 
Now the circuit can be shown as
Let current I flow in lower branch, so
1.25 I = 4V
I = 4/1.25 = 3.2 A
Therefore, 3.2 A current flows in 1 Ω resistance, hence potential difference between M and N is
V' = 3.2 x 1 = 3.2 volt
