Question 1

The main function of a fuse is to
A)protect the line
B)open the circuit
C)protect the appliance
D)prevent excessive currents

Accepted Answer

A fuse is designed to prevent excessive currents by breaking the circuit when the current exceeds a certain level, thus protecting the circuit and appliances from damage.

Question 2

On which of the following routine tests are conducted?
A)Oil circuit breakers
B)Air blast circuit breakers
C)Minimum oil circuit breakers
D)All of the above

Accepted Answer

Routine tests are conducted on all types of circuit breakers, including oil circuit breakers, air blast circuit breakers, and minimum oil circuit breakers. These tests are performed to ensure that the circuit breakers are operating properly and are able to protect the electrical system from faults.

Question 3

SF6 gas
A)is yellow in colour
B)is lighter than air
C)is nontoxic
D)has pungent small

Accepted Answer

SF6 (sulfur hexafluoride) is an inert, non-toxic gas. It is colorless, odorless, and heavier than air, making options A, B, and D incorrect.

Question 4

The arcing contacts in a circuit breaker are made of
A)copper tungsten alloy
B)porcelain
C)electrolytic copper
D)aluminium alloy

Accepted Answer

Copper tungsten alloy is used for arcing contacts in circuit breakers due to its high melting point, excellent conductivity, and resistance to welding and erosion under arcing conditions.

Question 5

Which of the following medium is employed for extinction of arc in air circuit breaker ?
A)Water
B)Oil
C)Air
D)SF6

Accepted Answer

Air circuit breakers use air as the medium for extinguishing the arc. The high velocity of air flow removes the heat from the arc path and helps in extinguishing it.

Question 6

With which of the following, a circuit breaker must be equipped for remote operation ?
A)Inverse time trip
B)Time-delay trip
C)Shunt trip
D)None of the above

Accepted Answer

A shunt trip is a device that allows a circuit breaker to be tripped remotely, enabling remote operation.

Question 7

Fault diverters are basically
A)fuses
B)relays
C)fast switches
D)circuit breakers

Accepted Answer

Fault diverters are essentially fast switches designed to quickly redirect electrical current in the event of a fault, ensuring the protection of the system by diverting the fault current away from sensitive components.

Question 8

A thermal protection switch can protect against
A)short-circuit
B)temperature
C)overload
D)over voltage

Accepted Answer

The answer of A thermal protection switch can protect against
A)short-circuit
B)temperature
C)overload
D)over...

Question 9

Arc in a circuit behaves as
A)a capackive reactance
B)an inductive reactance
C)a resistance increasing with voltage rise across the arc
D)a resistance decreasing with voltage rise across the arc

Accepted Answer

An arc in a circuit behaves as a resistance decreasing with voltage rise across the arc. This is because as the voltage increases, the arc becomes more conductive, effectively lowering its resistance.

Question 10

Thermal circuit breaker has
A)delayed trip action
B)instantaneous trip action
C)both of the above
D)none of the above

Accepted Answer

Thermal circuit breakers have a delayed trip action because they rely on the heat generated by the current to bend a bimetallic strip, which takes time to respond to overcurrent conditions.

Question 11

Relays can be designed to respond to changes in
A)resistance, reactance or impedance
B)voltage and current
C)light intensity
D)all above

Accepted Answer

Relays can be designed to respond to various changes including resistance, reactance, impedance, voltage, current, and light intensity, making all the options correct.

Question 12

Overload relays are of…… type.
A)induction
B)solid state
C)thermal
D)all above

Accepted Answer

Overload relays can be of various types including induction, solid state, and thermal, hence all the options listed are correct.

Question 13

Thermal overload relays are used to protect the motor against over current due to
A)short-circuits
B)heavy loads
C)grounds
D)all of the above

Accepted Answer

Thermal overload relays are specifically designed to protect motors from overheating due to excessive current draw, which can occur with heavy or prolonged loads. They are not designed to protect against short-circuits or ground faults, which are typically handled by circuit breakers or fuses.

Question 14

Magnetic circuit breaker has ______ trip action.
A)delayed
B)instantaneous
C)both of the above
D)none of the above

Accepted Answer

Magnetic circuit breakers have an instantaneous trip action, as they rely on the magnetic field generated by the current to trip the breaker immediately when the current exceeds a certain threshold.

Question 15

D.C. shunt relays are made of
A)few turns of thin wire
B)few turns of thick wire
C)many turns of thin wire
D)many turns of thick wire

Accepted Answer

D.C. shunt relays are made of many turns of thin wire to create a high resistance coil suitable for parallel connection across a voltage source.

Question 16

The relay operating speed depends upon
A)the spring tension
B)the rate of flux built up
C)armature core air gap
D)all of the above

Accepted Answer

The relay operating speed is influenced by multiple factors including the spring tension, the rate of flux buildup, and the armature core air gap. Each of these elements affects how quickly the relay can respond to changes, thus impacting its overall operating speed.

Question 17

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should
A)have low contact resistance
B)be clean and smooth
C)be of sufficient size and proper shape
D)have all above properties

Accepted Answer

All the mentioned properties are important for relay contacts to ensure efficient current flow without excessive heating or voltage drop. Low contact resistance minimizes energy loss, clean and smooth surfaces ensure good contact, and sufficient size and proper shape help handle the current load effectively.

Question 18

Circuit breakers usually operate under
A)transient state of short-circuit current
B)sub-transient state of short-circuit current
C)steady state of short-circuit current
D)after D.C. component has ceased

Accepted Answer

Circuit breakers are designed to operate during the transient state of short-circuit current to quickly interrupt the fault and protect the system.

Question 19

Circuit breakers are essentially
A)current carrying contacts called electrodes
B)arc extinguishers
C)circuits to break the system

Accepted Answer

Circuit breakers are devices that interrupt current flow in an electrical circuit, and they contain current carrying contacts called electrodes that open to break the circuit when necessary.

Question 20

The current zero interruption, in oil and air blast circuit breakers, is achieved by
A)lengthening of the gap
B)cooling and blast effect
C)both (a) and (b)
D)deionizing the oil with forced air

Accepted Answer

The current zero interruption in both oil and air blast circuit breakers is achieved through a combination of lengthening the gap between the contacts (which increases the distance the arc must travel, thus helping to extinguish it) and the cooling and blast effect (which rapidly cools the arc, reducing its temperature below the ionization point, and sweeps away the ionized particles).

Quiz 1: Electrical Components and Protective Relays

The main function of a fuse is to

On which of the following routine tests are conducted?

SF6 gas

The arcing contacts in a circuit breaker are made of

Which of the following medium is employed for extinction of arc in air circuit breaker ?

With which of the following, a circuit breaker must be equipped for remote operation ?

Fault diverters are basically

A thermal protection switch can protect against

Arc in a circuit behaves as

Thermal circuit breaker has

Relays can be designed to respond to changes in

Overload relays are of…… type.

Thermal overload relays are used to protect the motor against over current due to

Magnetic circuit breaker has ______ trip action.

D.C. shunt relays are made of

The relay operating speed depends upon

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should

Circuit breakers usually operate under

Circuit breakers are essentially

The current zero interruption, in oil and air blast circuit breakers, is achieved by