Basic Electrical Engineering MCQs Part 16

Basic Electrical Engineering MCQs Part 16

Electric current in a discharge tube containing gas is due which of following

Electric current in a discharge tube containing gas is due which of following:

  1. Positive ions only
  2. Electrons only
  3. Electrons and positive ions
  4. None of these

Correct answer: 3. Electrons and positive ions

At 0 K Germanium behaves as

At 0 K Germanium behaves as:

  1. Conductor
  2. Insulator
  3. Ferromagnetic
  4. Super conductor

Correct answer: 2. Insulator

Two resistors X and Y having resistance value Rx and Ry having resistivities ρx and ρy. If Rx < Ry, then

Two resistors X and Y having resistance value Rx and Ry having resistivities ρx and ρy. If Rx < Ry, then:

  1. Ρx = ρy
  2. ρx < ρy
  3. ρx > ρy
  4. Insufficient data

Correct answer: 4.Insufficient data

For a 10 kΩ resistor, the change in voltage when current changes from 2 mA to 5.5 mA is

For a 10 kΩ resistor, the change in voltage when current changes from 2 mA to 5.5 mA is:

  1. 35 V
  2. 50 V
  3. 70 V
  4. 120 V

Correct answer: 1. 35 V

Solution:

For resistor, the voltage versus current graph is linear.

When I = 2 mA; V = 20 V

When I = 5.5 mA; V = 55 V

Change in voltage = 55 V – 20 = 35 V

A carbon electrode has resistance of 0.12 Ω at 20°C. The temperature coefficient of carbon is -0.0005 at 20 °C. The value of resistance of electrode at 85°C is

A carbon electrode has resistance of 0.12 Ω at 20°C. The temperature coefficient of carbon is -0.0005 at 20 °C. The value of resistance of electrode at 85°C is:

  1. 0.1161
  2. 0.3255
  3. 0.9898
  4. 1.234

Correct answer: 1. 0.1161

Solution:

R2 = R1 [ 1 +  α(t 2- t1)]

R2 = 0.12 (1 + -0.0005 * (85 – 20))

R2 = 0.1161 Ω

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