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