JEE Main 2025 · 23 January · evening · Single correct · +4 / −1
What is the current through the battery in the circuit shown below?
- (a) 1.5 A
- (b) 0.25 A
- (c) 1.0 A
- (d) 0.5 A
Answer and solution
Answer (d) 0.5 A
Solution
Physics sir · 4 steps
Check the battery's polarity first: both diodes are forward biased, so they act as plain wires.
- Read the polarity. The longer plate of the battery is its positive terminal, and it is on the left. So current leaves the battery, goes up the left wire and enters both branches from the left.
- Diode check. Each diode's arrow points to the right, the same way the current wants to flow. Both are forward biased, so each ideal diode behaves like a wire with zero resistance.
- Combine resistors. Both branches conduct, so the two 20 Ω resistors are in parallel. Their equivalent is (20 × 20)/(20 + 20) = 10 Ω.
I = V/R_(eq) = (5 V)/(10 Ω) = 0.5 A
- So. The battery supplies 0.5 A, which splits as 0.25 A through each branch. That is option (d).
The idea to keep. With diodes in a circuit, first decide which way each diode points relative to the battery. Forward biased means a short wire, reverse biased means a broken branch. Then solve the leftover resistor network.
Answer from the NTA final answer key. Solution by PrepWiser.