Basic Electrical Engineering MCQs Part 3

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Basic Electrical Engineering MCQs Part 3

A substance having number of valence electrons equal to 4 is usually

A substance having number of valence electrons equal to 4 is usually

  1. An insulator
  2. A semiconductor
  3. A conductor
  4. None of the above

Correct answer: 2. A semiconductor

Constantan wire is used for making standard resistor since it has

Constantan wire is used for making standard resistor since it has:

  1. High specific resistance
  2. Low specific resistance
  3. High melting point
  4. Negligibly small temperature coefficient of resistance

Correct answer: 4. Negligibly small temperature coefficient of resistance

The specific resistance of material of wire depends on

The specific resistance of material of wire depends on:

  1. Mass
  2. Length
  3. Area of cross-section
  4. None of these

Correct answer: 4. None of these

Explanation: Electrical resistivity also known as specific electrical resistance or volume resistivity is a fundamental property of a material that measures how strongly it resists electric current. The specific resistance of material of wire depends on the material from which it is fabricated and it doesn’t depends on the mass, length or area of cross-section of material.

Electric current in liquids is due to flow of

Electric current in liquids is due to flow of:

  1. Electrons
  2. Positive ions
  3. Negative ions
  4. 2 and 3

Correct answer: 4. 2 and 3

An electron is moving in cirlce of radius 4.5*10^-11 m at a frequency of 5.28*10^15 revolutions per second. The equivalent current is approximately

An electron is moving in cirlce of radius 4.5*10^-11 m at a frequency of 5.28*10^15 revolutions per second. The equivalent current is approximately:

  1. 4.2 * 10^-4 A
  2. 2.3 * 10^-4 A
  3. 5.86 * 10^-4 A
  4. 8.45 * 10^-4 A

Correct answer: 4. 8.45 * 10^-4 A

Solution:

Current = Charge/Time period = Charge * Frequency

=1.6810^-19 * 5.28*10^15 = 8.45 * 10^-4 A

The drift velocity of free electrons is of the roder:

  1. 1 m/s
  2. 10^-3 m/s
  3. 10^-5 m/s
  4. 10^-9 m/s

Correct answer: 3. 10^-5 m/s

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