Current Electricity

71. The thickness of insulation provided on the conductor depends on

1. the magnitude of voltage on the conductor
2. the magnitude of current flowing through it
3. both (a) and (b)
4. none of the above

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72. The weight of an aluminium conductor as compared to a copper conductor of identical cross-section, for the same electrical resistance, is

1. 50%
2. 60%
3. 100%
4. 150%

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73. Three 6 ohm resistors are connected to form a triangle. What is the resistance between any two corners?

1. 3/2 Q
2. 6 Q
3. 4 Q
4. 8/3 Q

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74. Three 60 W bulbs are in parallel across the 60 V power line. If one bulb burns open

1. there will be heavy current in the main line
2. rest of the two bulbs will not light
3. all three bulbs will light
4. the other two bulbs will light

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75. Three identical resistors are first connected in parallel and then in series. The resultant resistance of the first combination to the second will be

1. 9 times
2. 1/9 times
3. 1/3 times
4. 3 times

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76. Three resistances of 10 ohms, 15 ohms and 30 ohms are connected in parallel. The total resistance of the combination is

1. 5 ohms
2. 10 ohms
3. 15 ohms
4. 55 ohms

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77. Two bulbs of 500 W and 200 W rated at 250 V will have resistance ratio as

1. 4 : 25
2. 25 : 4
3. 2 : 5
4. 5 : 2

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78. Two copper conductors have equal length. The cross-sectional area of one conductor is four times that of the other. If the conductor having smaller cross- sectional area has a resistance of 40 ohms the resistance of other conductor will be

1. 160 ohms
2. 80 ohms
3. 20 ohms
4. 10 ohms

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79. Two lamps 100 W and 40 W are connected in series across 230 V (alternating). Which of the following statement is correct?

1. 100 W lamp will glow brighter
2. 40 W lamp will glow brighter
3. Both lamps will glow equally bright
4. 40 W lamp will fuse

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80. Two resistances Rl and Ri are connected in series across the voltage source where Rl>Ri. The largest drop will be across

1. Rl
2. Ri
3. either Rl or Ri
4. none of them

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