Questions
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 |
detailed solution
Correct option is A
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.Talk to our academic expert!
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A resistor R is connected across a battery of emf 12 V. It observed that terminal potential differenceis 9 V and the power delivered to resistor is 18 W. Internal resistance of the battery ‘r’ and the resistance R are respectively
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