Question

Boojho made the circuit given in the figure and observed that the bulb did not glow. On Paheli’s suggestion he added one more cell in the circuit. The bulb now glows. Explain.

Answer 1

Initially, the bulb was not glowing because the voltage required to make the bulb glow was not sufficient. With the addition of another cell, the voltage increases, i.e. the current through the bulb increases more than a particular value and the bulb starts glowing because it gets sufficient energy to heat its filament.