Answer :
When L1 and L2 are in series and L1 opens, both lamps would be off because in a series circuit, a failure in one component interrupts the current flow to all other components. Thus option d. is correct.
If two lamps, L1 and L2, are connected in series and L1 opens (fails), then the correct answer is d. Both lamps would be off. In a series circuit, the current follows a single path, and if one component fails, it interrupts the flow of current to all other components in the same loop. This is similar to having a break in a single water pipe that stops water flow to all taps connected in series to that pipe.
Since L1 has opened, no current can flow through L1 or L2, making it impossible for either lamp to light up. Series circuits are characterized by this dependence of each component on the continuous path of the circuit. Unlike in parallel circuits, where components are connected across common points and each has a separate path to the power source, a failure in a series circuit affects the entire circuit. Thus option d. is correct.
