Question

An incandescent lamp was connected to an electric circuit but it did not glow. Which of the following could not be a valid reason for the bulb not glowing?

• A. The switch in the circuit was not closed.
• B. The positive and negative terminals of the battery were interchanged.
• C. The filament of the bulb was burnt out.
• D. The battery was out of power.

Answer 1

The correct option is B The positive and negative terminals of the battery were interchanged.

There will be no current in the circuit if the switch is not closed or if the battery is out of power. Hence the bulb will not glow. A bulb cannot glow when its filament inside the bulb is broken.
If the polarity of the cell is reversed, only the direction of current flow changes. The bulb will still glow as there is nothing like positive and negative terminal of the bulb.