40 Important Magnetic Circuit MCQ Question and Answer | PDF Free Download
1.An air gap is usually inserted in magnetic circuits to
- AIncrease m.m.f
- BIncrease the flux
- CPrevent saturation
- DNone of the above
2.The relative permeability of a ferromagnetic material is
- ALess than one
- BMore than one
- CMore than 10
- DMore than 100 or 1000
3.The unit of magnetic flux is
- AHennery
- BWeber
- CAmpere-turn/weber
- DAmpere/meter
4.Permeability of a magnetic circuit corresponds to____________ In an electrical circuits.
- AResistance
- BResistivity
- CConductivity
- DConductance
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
6.Permanent magnets are normally made of
- AAlnico alloys
- BAluminium
- CCast iron
- DWrought iron
7.Energy stored by a coil is doubled when its current is increased by ???.percent.
- A25
- B50
- C41.4
- D100
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
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
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
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
12.A material for good magnetic memory should have
- ALow hysteresis loss
- BHigh permeability
- CLow retentivity
- DHigh retentivity
13.Conductivity is analogous to
- ARetetnivity
- BResistivity
- CPermeability
- Dinductance
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
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
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
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
18.Silicon steel is used in electrical machines because it has
- ALow co-ercivity
- BLow retentivity
- CLow hysteresis
- DHigh co-ercivity
20.Conductance is analogous to
- APermanence
- BReluctance
- CFlux
- DInductance