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JEE Main 2026 · 5 Apr · Shift 1, Physics question 45

For the given logic circuit, which of the following inputs combination will make both LED-1 and LED-2 to glow?

A and B feed an OR gate whose output drives LED-1 (through a resistor to ground) and goes to an AND gate together with input C. That AND output and input A (via a wire along the top) feed a second AND gate, whose output drives LED-2.
Choose one option
Answer and worked solution

Official answer: C

The two LEDs.

  • LED-1: lit when A+B=1A+B=1.
  • LED-2: lit when A⋅(C⋅(A+B))=1A\cdot\big(C\cdot(A+B)\big)=1, which needs A=1A=1 and C=1C=1.

Check A = 1, B = 0, C = 1. A+B=1A+B=1 (LED-1 on) and A C (A+B)=1A\,C\,(A+B)=1 (LED-2 on). Each other option has A=0A=0 or C=0C=0, so LED-2 stays off.

(C)

Topics:Logic gates
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