Practice portal › Current Electricity › Resistance and Resistivity

Consider two circuits, (A) and (B), each having two resistors. One of them has a positive temperature coefficient of resistance, +α, while the other one has a negative temperature coefficient, -α, as shown in the figure. The current through these circuits are denoted by I_A and I_B. At initial temperature, the resistance of the two resistors is R₀. As the temperature is increased, the correct option that describes the variation of current in these circuits is :

Asked in Re-NEET 2026 · Temperature dependence of resistance

• (1) I_A remains constant while I_B increases
• (2) I_A decreases while I_B increases
• (3) I_A increases while I_B decreases
• (4) both I_A and I_B remain constant

Step-by-step solution

Why the other options are wrong

• (2) In series the changes cancel exactly: R_A=R₀(1+αΔ T)+R₀(1-αΔ T)=2R₀, so I_A does not change.
• (3) Both parts are reversed: I_A stays constant, and R_B falls, so I_B rises.
• (4) I_A is constant, but in parallel the changes do not cancel: R_B=(R₀)/2(1-α²Δ T²) falls, so I_B rises.

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.