Question

A simple circuit consists of a battery and a light bulb. A second identical light bulb is then added in series to the first light bulb.
What affect does this have on the brightness of the first light bulb?

• A. The brightness gets brighter.
• B. The light bulb goes out.
• C. The brightness gets dimmer.
• D. The brightness does not change.

Answer 1

Answer: (C)

The brightness gets dimmer.

As the second identical bulb (having same resistance) is connected in series with first bulb, therefore total resistance of the circuit increases hence total current will decrease and by

$P=I^{2}R$

or $P\propto I^2$ ,

it means power dissipation in first bulb decreases i.e. brightness of first bulb gets dimmer .