Switchgear and Protection MCQs Part 3. Multiple choice questions on Switchgear and Protection.

Contents

- 1 Commonly the making current of the circuit breaker is expressed in terms of
- 2 The rating of fuse is expressed in terms of
- 3 Under normal operating conditions the contacts of the circuit breaker remain
- 4 In case of forced blast circuit breaker, the speed of circuit interruption is
- 5 On switching off the load sparking occurs due to high current
- 6 The circuit breaker must be able to perform the action of
- 7 An isolator is designed to open a circuit under condition of
- 8 If length of the arc in a circuit breaker increases, its resistance
- 9 The time-current graph of a fuse
- 10 For the same power, which of following circuit breaker has least size

## Commonly the making current of the circuit breaker is expressed in terms of

Commonly the making current of circuit breaker is expressed in terms of:

- Average value
- Peak value
- RMS value
- None of these

Correct answer: 2. Peak value

## The rating of fuse is expressed in terms of

The rating of fuse is expressed in terms of:

- Amperes
- Volts
- Volt-amperes
- kVAR

Correct answer: 1. Amperes

## Under normal operating conditions the contacts of the circuit breaker remain

Under normal operating conditions the contacts of the circuit breaker remain:

- Semi-closed
- Closed
- Open
- None of above

Correct answer: 2. Closed

## In case of forced blast circuit breaker, the speed of circuit interruption is

In case of forced blast circuit breaker, the speed of circuit interruption is:

- Fast
- Medium
- Slow
- None of these

Correct answer: 1. Fast

## On switching off the load sparking occurs due to high current

On switching off the load sparking occurs due to high current:

- Resistance
- Capacitance
- Inductance
- Skin effect

Correct answer: 3. Inductance

## The circuit breaker must be able to perform the action of

The circuit breaker must be able to perform the action of:

- Breaking fault current
- Opening faulty circuit
- Carrying fault current for short time
- All of these

Correct answer: 4. All of these

## An isolator is designed to open a circuit under condition of

An isolator is designed to open a circuit under condition of:ยท

- Nom1al flow
- Full load
- No load
- None of these

Correct answer: 3. No load

## If length of the arc in a circuit breaker increases, its resistance

If length of the arc in a circuit breaker increases, its resistance:

- Increases
- Decreases
- Remains same
- None of above

Correct answer: 1. Increases

## The time-current graph of a fuse

The time-current graph of a fuse

- Is a straight line
- Has inverse characteristic
- Is a circle
- None of these

Correct answer: 2. Has inverse characteristic

## For the same power, which of following circuit breaker has least size

For the same power, which of following circuit breaker has least size:

- Vacuum circuit breaker
- SF6 circuit breaker
- Oil circuit breaker
- Air-blast circuit breaker

Correct answer: 2. SF6 circuit breaker