Magnetic Circuit MCQ Question Answer

Magnetic Circuit MCQ Question and Answer

1.An air gap is usually inserted in magnetic circuits to

  • AIncrease m.m.f
  • BIncrease the flux
  • CPrevent saturation
  • DNone of the above
Answer / Hint Save Question Comment On Question
Correct Answer : (C)

Prevent saturation

Explanation:

An air gap is usually inserted in magnetic circuits to Prevent saturation.

2.The relative permeability of a ferromagnetic material is

  • ALess than one
  • BMore than one
  • CMore than 10
  • DMore than 100 or 1000
Answer / Hint Save Question Comment On Question
Correct Answer : (D)

More than 100 or 1000

Explanation:

The relative permeability of a ferromagnetic material is More than 100 or 1000.

3.The unit of magnetic flux is

  • AHennery
  • BWeber
  • CAmpere-turn/weber
  • DAmpere/meter
Answer / Hint Save Question Comment On Question
Correct Answer : (B)

Weber

Explanation:

The unit of magnetic flux is Weber.

4.Permeability of a magnetic circuit corresponds to???. In an electrical circuits

  • AResistance
  • BResistivity
  • CConductivity
  • DConductance
Answer / Hint Save Question
Correct Answer : (C)

Conductivity

Explanation:

5.Point out the wrong statement.Magnetic leakage is undesirable inn electric machine because it

  • ALower their power efficiency
  • BIncreases their cost of manufacture
  • CLeads to their increased weight
  • DProduces fringing
Answer / Hint Save Question
Correct Answer : (A)

Lower their power efficiency

Explanation:

6.Permanent magnets are normally made of 

  • AAlnico alloys
  • BAluminium
  • CCast iron
  • DWrought iron
Answer / Hint Save Question Comment On Question
Correct Answer : (A)

Alnico alloys

Explanation:

Permanent magnets are normally made of Alnico alloys.

7.Energy stored by a coil is doubled when its current is increased by ???.percent.

  • A25
  • B50
  • C41.4
  • D100
Answer / Hint Save Question Comment On Question
Correct Answer : (C)

41.4

Explanation:

Energy stored by a coil is doubled when its current is increased by 41.4 percent.

8.Those magnetic materials are best suited for making armature and transformer cores should have

  • AHigh permeability, high hysteresis loss
  • BLow permeability, high hysteresis loss
  • CHigh permeability, Low hysteresis loss
  • DLow permeability, Low hysteresis loss
Answer / Hint Save Question Comment On Question
Correct Answer : (C)

High permeability, Low hysteresis loss

Explanation:

Those magnetic materials are best suited for making armature and transformer cores should have High permeability, Low hysteresis loss.

9.The rate of rise of current through an inductive coil is maximum

  • AAt 63.2% of its maximum steady value
  • BAt the start of the current flow
  • CAfter one time constant
  • DNear the final maximum value of current
Answer / Hint Save Question Comment On Question
Correct Answer : (B)

At the start of the current flow

Explanation:

The rate of rise of current through an inductive coil is maximum At the start of the current flow.

10.When both the inductance and resistance of the coil are doubled the value of

  • ATime constant remains unchanged
  • BInitial rate of rise of current is doubled
  • CFinal steady current is doubled
  • DTime constant is halved
Answer / Hint Save Question Comment On Question
Correct Answer : (A)

Time constant remains unchanged

Explanation:

When both the inductance and resistance of the coil are doubled the value of Time constant remains unchanged.

11.The initial rate of rise of current through a coil of inductance 10H when suddenly connected to a D.C. supply of 200 V  is ?? A/s

  • A50
  • B20
  • C0.05
  • D500
Answer / Hint Save Question
Correct Answer : (B)

20

Explanation:

12.A material for good magnetic memory should have

  • ALow hysteresis loss
  • BHigh permeability
  • CLow retentivity
  • DHigh retentivity
Answer / Hint Save Question Comment On Question
Correct Answer : (D)

High retentivity

Explanation:

A material for good magnetic memory should have High retentivity.

13.Conductivity is analogous to

  • ARetetnivity
  • BResistivity
  • CPermeability
  • Dinductance
Answer / Hint Save Question
Correct Answer : (C)

Permeability

Explanation:

14.In a magnetic material hysteresis loss takes place primarily due to

  • ARapid reversals of its magnetization
  • BFlux density lagging behind magnetising force
  • CMolecular friction
  • DIt's high retentivity
Answer / Hint Save Question Comment On Question
Correct Answer : (D)

It's high retentivity

Explanation:

In a magnetic material hysteresis loss takes place primarily due to It's high retentivity.

15.Those materials are well suited for making permanent magnets should have

  • ALow retentivity, high Coercivity
  • BHigh retentivity, high Coercivity
  • CHigh retentivity, low Coercivity
  • DLow retentivity, low Coercivity
Answer / Hint Save Question Comment On Question
Correct Answer : (B)

High retentivity, high Coercivity

Explanation:

Those materials are well suited for making permanent magnets should have High retentivity, high Coercivity.

16.If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be

  • AZero
  • Bsmall
  • CLarge
  • DNone of the above
Answer / Hint Save Question Comment On Question
Correct Answer : (C)

Large

Explanation:

If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be Large.

17.Hard steel is suitable for making permanent magnets because

  • AIt has good residual magnetism
  • BIts hysteresis loop has large area
  • CIts mechanical strength is high
  • DIts mechanical strength is low
Answer / Hint Save Question Comment On Question
Correct Answer : (A)

It has good residual magnetism

Explanation:

Hard steel is suitable for making permanent magnets because It has good residual magnetism.

18.Silicon steel is used in electrical machines because it has

  • ALow co-ercivity
  • BLow retentivity
  • CLow hysteresis
  • DHigh co-ercivity
Answer / Hint Save Question Comment On Question
Correct Answer : (C)

Low hysteresis

Explanation:

Silicon steel is used in electrical machines because it has Low hysteresis.

19.q

  • Aq
  • Bq
  • Cq
  • Dq
Answer / Hint Save Question
Correct Answer : (A)

q

Explanation:

20.Conductance is analogous to

  • APermanence
  • BReluctance
  • CFlux
  • DInductance
Answer / Hint Save Question
Correct Answer : (A)

Permanence

Explanation: