Consider two circuits, (A) and (B), each having two resistors. One of… | NEET 2026 (Re-neet)

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Ohm's Law, Resistivity & Temperature

Consider two circuits, (A) and (B), each having two resistors. One of them has a positive temperature coefficient of resistance, $+\alpha$ , while the other one has a negative temperature coefficient, $-\alpha$ , as shown in the figure. The currents through these circuits are denoted by $I_A$ and $I_B$ . At initial temperature, the resistance of the two resistors is $R_0$ . As the temperature is increased, the correct option that describes the variation of current in these circuits is:

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Answer: (b)

Circuit A (series): $R_A = R_0(1-\alpha\Delta T) + R_0(1+\alpha\Delta T) = 2R_0$ , independent of temperature.
So $I_A = V/2R_0$ stays constant.
Circuit B (parallel): $R_B = \dfrac{R_0^2(1-\alpha^2\Delta T^2)}{2R_0} = \dfrac{R_0}{2}(1-\alpha^2\Delta T^2)$ , which decreases as $\Delta T$ rises.
So $I_B = V/R_B$ increases. The answer is (b).

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