Question

In the circuit given below, identify the lamp (L₁, L2, L₃ or L₄) whose failure would not interrupt the power supply to the other lamps.

Options

• L₁

• L₂

• L₃

• L₄

Answer 1

L₂

Explanation:

The circuit has L₁ in series with a parallel combination of L₂ and the series combination of L₃ and L₄.

If L₁ fails, the entire circuit is broken, and no current flows to any other lamp. If L₃ or L₄ fails, the series path containing both L₃ and L₄ is broken. L₂ is in a separate parallel branch, so it will continue to receive power and stay lit. If L₂ fails, the parallel branch containing only L₂ is broken. Current can still flow through the branch with L₃ and L₄, so L₁, L₃, and L₄ will remain lit.

Therefore, the failure of L₂ is the only case where all the other lamps (L₁, L₃, and L₄) continue to receive power and stay lit.