First slide

Electrical power

Question

The circuit shown in figure, contains a battery, a rheostat and two identical lamps. What will happen to the brightness of the lamps if the resistance of the rheostat is increased?
Lamp P Lamp Q
(a) Less brighter Brighter
(b) Less brighter Less brighter
(c) Bright Less brighter
(d) No change Brighter

Moderate

A

Lamp P Lamp Q
Less brighter Brighter
B

Lamp P Lamp Q
Less brighter Less brighter
C

Lamp P Lamp Q
Bright Less brighter
D

Lamp P Lamp Q
No change Brighter

Solution

Consider two extreme cases. (i) When the resistance of the rheostat is zero, the current through O is zero since 0 is short-circuited. The circuit is then essentially a battery in series with lamp P. (ii) When the resistance of the rheostat is very large, almost no current flows through it. So, the currents through P and Q are almost equal. The circuit is essentially a battery in series with lamps P and Q.

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App