Figure represent a part of a closed circuit. The potential difference between . . .

Question : Figure represent a part of a closed circuit. The potential difference between points A and B (V_A-V_B) is

a) +9V

b) -9V

c) +3V

d) +6V

Doubt by Jayant

Solution :

V_A-V_B = ?

I=2 A

Applying Kirchhoff's Voltage Law

V_A-I(2)-3-I(1)-V_B=0
V_A-2(2)-3-2(1)-V_B=0
V_A-4-3-2-V_B=0
V_A-9-V_B=0
V_A-V_B=9
∴ V_A-V_B=+9V

Hence, a) would be the correct option.

Note : Because the current is flowing from A to B it indicates that potential at A (VA) must be greater than potential at B (VB). So VA-VB=+ve

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