Q. No.A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected across the given cell, has values of (i) infinity (ii) 9.5, the 'balancing lengths, on the potentiometer wire, are found to be 3m and 2.85 m, respectively.
The value of internal resistance of the cell is (in ohm) :
1. 0.25
2. 0.95
3. 0.5
4. 0.75
The value of internal resistance of the cell is (in ohm) :
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A set of 'n' equal resistors, of value 'R' each, are connected in series to a battery of emf 'E' and internal resistance 'R'. The current drawn is I. Now, the 'n' resistors are connected in parallel to the same battery. Then the current drawn becomes 10I. The value of 'n' is:-
1. 10
2. 11
3. 20
4. 9
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Which of the following acts as a circuit protection device?
1. fuse
2. conductor
3. inductor
4. switch
Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volt and the average resistance per km is 0.5 The power loss in the wire is:
1. 19.2 W
2. 19.2 kW
3. 19.2 J
4. 12.2 kW
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2. 40
3. 44
4. 48
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2. flow in the direction which will be decided by the value of V
3. be zero
4. flow from B to A
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If voltage across a bulb rated 220 V-100 W drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is :
1. 20%
2. 2.5%
3. 5%
4. 10%
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2. 3
3. 61
4. 6
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The resistance of an ammeter is 13 Ω and its scale is graduated for a current up-to 100 A. After an additional shunt has been connected to this ammeter it becomes possible to measure currents up-to 750 A by this meter. The value of shunt resistance is:
1. 20
2. 2
3. 0.2
4. 2 k
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A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is approximately :
1. 30%
2. 50%
3. 90%
4. 10%
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