Basic Electrical Engineering

11. A current surge takes place when a power supply is first turned on because

1. the transformer core is suddenly magnetized
2. the diodes suddenly start to conduct
3. the filter capacitor must be initially charged
4. arching takes place in the power switch

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12. A dc electromagnet

1. has constant polarity
2. Requires an air core
3. Cannot be used to permanently magnetize anything
4. Does not attract or repel permanent magnet

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13. A dc to dc converter having an efficiency of 80% is delivering 16W to a load. If the converter is generating an output of 200V from an input source of 20V, then the current drawn from the source will be?

1. 0.1A
2. 0.5A
3. 1.0A
4. 10.0A

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14. A degree of phase represents

1. 6.28 cycles
2. 57.3 cycles
3. 1/60 of a cycle
4. 1/360 of a cycle

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15. A ferromagnetic core is place in the inductor to

1. Increase the current carrying capacity
2. Increase the inductance
3. Limit the current
4. Reduce the inductance

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16. A flute sounds different than a violin, even if the two instruments are played at the same pitch, because of a difference in the

1. Phase
2. Chamber length
3. Frequency
4. Waveform
5. Bias

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17. A house served by a 220V supply light, is protected by a 9-Ampere fuse. The maximum number of 60 W bulbs in parallel that can be turned on is

1. 11
2. 33
3. 22
4. 44

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18. A material with a high dielectric constant

1. Acts to increase capacitance per unit volume
2. Acts to decrease capacitance per unit volume
3. Has no effect on capacitance
4. Causes a capacitor to become polarized

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19. A network that does not have either voltage or current source is called network

1. Active
2. Passive
3. Resistive
4. Dummy

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20. A phase difference of 180deg in the circular motion model of a sine wave represents

1. ¼ revolution
2. ½ revolution
3. A full revolution
4. Two full revolution

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