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In the given circuit, potential difference between points P and Q is ________.

Asked in GUJCET 2025 · Series and parallel combinations

Figure: Series and parallel combinations
Answer: (2) 20 V

Step-by-step solution

Given: a +60 V rail and a 0 V rail with 64 Ω and 32 Ω in series between them. P is tapped off between the two resistors and Q below the 32 Ω resistor, at the bottom rail.

Idea: P and Q are open terminals, so no current is drawn from them. The supply therefore drives one single loop through the two resistors in series, and V_PQ is just the drop across the 32 Ω resistor.

Total resistance: 64 + 32 = 96 Ω.

Current: I = (60)/(96) = 0.625 A.

V_PQ = I×32 = 0.625×32 = 20 V.

As a check, the 64 Ω resistor takes the other 40 V, and 40 + 20 = 60 V, the whole supply.

So the potential difference between P and Q is 20 V.

Why the other options are wrong

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