Q. No.Two cells of equal e.m.f. and of internal resistances, r1, and are connected in series. On connecting this combination to an external resistance R, it is observed that the potential difference across the first cell becomes zero. The value of R will be :
(1)
(2)
(3)
(4)
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A battery is charged at a potential of 15 V for 8 hours when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 hours. The mean terminal voltage during discharge is 14 V. The "Watt-hour" efficiency of the battery is :
(1) 82.5%
(2) 80 %
(3) 90%
(4) 87.5%
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A potentiometer wire is 100 cm long and a constant potential is maintained across it. Two cells are connected in series first to support one another and then in the opposite direction. The balance points are obtained at 50 cm and 10 cm from the positive end of the wire in the two cases. The ratio of emf is
1. 5:4 2. 3:4
3. 3:2 4. 5:1
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In order to quadruple the resistance of a uniform wire, a part of its length was uniformly stretched till the final length of the entire wire was 1.5 times the original length, the part of the wire was a fraction equal to:
(1) 1/8
(2) 1/6
(3) 1/10
(4) 1/4
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The internal resistances of the two cells shown are 0.1 Ω and 0.3 Ω. If R = 0.2 Ω, the potential difference across the cell :
(1) B will be zero
(2) A will be zero
(3) A and B will be 2V
(4) A will be > 2V and B will be < 2V
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A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/ quantities constant along the length of the conductor is/are :
(1) Current, electric field and drift speed
(2) Drift speed only
(3) Current and drift speed
(4) Current only
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In the circuit element given here, if the potential at point B, VB = 0, then the potentials of A and D are given as
(1)
(2)
(3)
(4)
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1. \(0.25~\text{A}\)
2. \(0.8~\text{A}\)
3. \(0.2~\text{A}\)
4. \(0.5~\text{A}\)
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As the switch S is closed in the circuit shown in the figure, the current passed through it is:
(1) 4.5 A
(2) 6.0 A
(3) 3.0 A
(4) Zero
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In given figure, the potentiometer wire AB has a resistance of 5 Ω and length 10 m. The balancing length AM for the emf of 0.4 V is :
(1) 0.4 m
(2) 4 m
(3) 0.8 m
(4) 8 m
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