Three incandescent bulbs of 100 W each are connected in series in an electric circuit. In another circuit, another set of three bulbs of the same wattage are connected in parallel to the same source.
(а) Will the bulb in the two circuits glow with the same brightness? Justify your answer.
(b) Now let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.
For three identical bulbs,
In series, Rs = 3R
In parallel, Rp = R/3
(a) The bulbs in the two circuits will not glow equally bright as the current through them is not the same.
In series, Is = V/Rs = V/3R
In parallel, Ip = V/(R/3) = 3V/R
So, Ip > Is
(b) As one bulb fuses, the other bulbs in the series circuit will not glow because the circuit becomes an open circuit. While the rest of bulbs in parallel circuit will continue to glow without getting disturbed because in parallel combination, current gets additional paths to flow.