Quiz: Electrical Engineering 6 April 2020

Quiz: Electrical Engineering

Exam: NLC

Topic: Miscellaneous

 

Each question carries 1 mark.

Negative marking: 1/4 mark

Time: 10 Minute

 

Q1. Which semiconductor device behaves like two SCR’s?

(a) Triac

(b) MOSFET

(c) JEET

(d) UJT

L1Difficulty 3

QTags Semiconductors & diodes

QCreator Balwant Kumar

 

 

Q1.   A switchgear is device used for

(a) interrupting an electrical circuit

(b) switching an electrical circuit

(c) switching and controlling an electrical circuit

(d) switching, controlling and protecting the electrical circuit and equipment

L1Difficulty 3

QTags Switchgear and protection

QCreator Balwant Kumar

 

 

 

Q3.   The insulating material for a cable should have

(a) low cost

(b) high dielectric strength

(c) high mechanical strength

(d) all of the above

L1Difficulty 3

QTags Switchgear and protection

QCreator Balwant Kumar

 

 

 

 

Q4.   Cables, generally used beyond 66 kV are

(a) oil filled

(b) S.L. type

(c) belted

(d) Armoured

L1Difficulty 3

QTags Utilization of electrical energy

QCreator Balwant Kumar

 

 

Q5.      Reciprocal of permeability is

(a) reluctivity

(b) susceptibility

(c) permittivity

(d) conductance

L1Difficulty 3

QTags Basic electrical engineering

QCreator Balwant Kumar

 

 

Q6.      A transformer provides a path of magnetic flux of

(a) high conductivity

(b) high reluctance

(c) low reluctance

(d) low conductivity

L1Difficulty 3

QTags Transformer

QCreator Balwant Kumar

 

 

 

Q7.      Which of the following is not a unit of flux?

(a) Maxwell

(b) Tesla

(c) Weber

(d) All of the above

L1Difficulty 3

QTags Magnetic circuit

QCreator Balwant Kumar

 

 

Q8.      Transformer works on the principle of

(a) gauss law

  1. b) self-induction

(c) Faraday’s law of electromagnetic inductions

(d) self and mutual induction both

L1Difficulty 3

QTags Transformer

QCreator Balwant Kumar

 

 

Q9.      Which of the following statements is correct?

(a) The magnetic flux inside an exciting coil is lower than its outside surface

(b) The magnetic flux inside an exciting coil is zero

(c) The magnetic flux inside the exciting coil is greater than its outside surface

(d) The magnetic flux inside the exciting coil is same as on its outside surface

L1Difficulty 3

QTags Magnetic circuit

QCreator Balwant Kumar

 

 

Q10.      In an induction motor, the torque T is related to the supply voltage V as

(a) T  V

(b) T  V²

(c) T

(d) T

L1Difficulty 3

QTags Single phase induction motor

QCreator Balwant Kumar

 

 

Solution

 

 

S1. (a)

sol.  Triac

 

S2. (d)

SOL

In an electric power system, switchgear is the combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream. This type of equipment is directly linked to the reliability of the electricity supply.

 

S3. (d)

Solution: The insulating materials used in cables should have the following properties:

  • High insulation resistance to avoid leakage current.
  • High dielectric strength to avoid electrical breakdown of the cable.
  • High mechanical strength to withstand the mechanical handling of cables.
  • Non-hygroscopic i.e., it should not absorb moisture from air or soil. The moisture tends to decrease the insulation resistance and hastens the breakdown of the cable. In case the insulating material is hygroscopic, it must be enclosed in a waterproof covering like lead sheath.
  • Non-inflammable.
  • Low cost so as to make the underground system a viable proposition.
  • Unaffected by acids and alkalis to avoid any chemical action

 

S4. (a)

Solution:

Cables generally used beyond 66 kV are oil filled.

 

S5. (a)

Reluctivity is reciprocal of permeability.

S6. (c)

Low reluctance

; As  increases Reluctance decreases.

 

S7. (b)

Tesla is the unit of magnetic flux density. (1 tesla = 1 wb/sq.m)

S8. (a)

Transformer works on the principle of Faraday’s law of electromagnetic inductions.

S9. (d)

Magnetic flux inside and outside surface of an exciting coil is same.

S10. (b)

Relation between torque and supply voltage of an induction motor

T  V²

 

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