Electricity and Magnetic Fundamentals

71. How is mutual inductance between two coils decreased?

1. By using a common core
2. By moving the coils closer
3. By moving the coils apart
4. By increasing the number of turns of either coil

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72. How many electrons are needed in the valence orbit to give a material's stability?

1. 8
2. 4
3. 6
4. 5

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73. How many neutrons does a copper atom have?

1. 32
2. 33
3. 34
4. 29

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74. How many turns are needed to produce a magnetomotive force of 1000 A.t for a coil with 6 amperes?

1. 6000 turns
2. 600 turns
3. 167 turns
4. 67 turns

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75. How much is the flux in Weber in the above problem?

1. 2 x 10∧-5
2. 2 x 10∧-3
3. 2 x 10∧5
4. 2 x 10∧3

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76. Hydrogen is an example of a _________ material.

1. Paramagnetic
2. Diamagnetic
3. Ferromagnetic
4. Non- magnetic

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77. Hysteresis refers to the _________between flux density of the material and the magnetizing force applied.

1. Leading effect
2. Ratio
3. Equality
4. Lagging effect

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78. Hysteresis is a phenomenon of _________ in a magnetic circuit.

1. setting up constant flux
2. lagging of H behind B
3. lagging B behind H
4. leading B ahead H

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79. Hysteresis loss can be reduced by one of the following.

1. Increasing mmf of the circuit
2. Using material narrow hysteresis loop
3. Using ferromagnetic core
4. Laminating the magnetic circuit

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80. If a 20 V potential is applied across a relay coil with 50 turns having 1 Ω of resistance, the total magnetomotive producing magnetic flux in the circuit is

1. 10 Wb
2. 50 T
3. 1000 A t/m
4. 1OOO A.t

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