In the circuit shown in the figure (A), R 3 is a variable resistance. As the value R 3 is changed, the current I through the cell varies as shown in the figure (B). As R 3 → ∞ , the current I → 6 A . What is the value of the sum of the resistances R 1 and R 2 in ohms?

Question

In the circuit shown in the figure (A), R 3 is a variable resistance. As the value R 3 is changed, the current I through the cell varies as shown in the figure (B). As R 3 → ∞ , the current I → 6 A . What is the value of the sum of the resistances R 1 and R 2 in ohms?,

MARKS App · Accepted Answer

For R 3 = 0 , I = 9 A (from the graph).In this situation, the circuit can be drawn as shown in figure A . [current through R 2 will be zero because we have a short circuit R 3 = 0 across R 2 ] Here I = 36 R 1 + R 2 = 9 A R 1 + R 2 = 4 Ω

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