Q.1
For a given wirewound core, an increase in current through the coil
  • reverses the flux lines
  • decreases the flux density
  • increases the flux density
  • causes no change in flux density
Q.2
The induced voltage across a coil withturns that is located in a magnetic field that is changing at a rate of 8 Wb/s is
  • 1,000 V
  • 2,000 V
  • 31.25 V
  • 3,125 V
Q.3
When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage
  • increases
  • decreases
  • remains constant
  • reaches zero
Q.4
The rate of rise of current through an inductive coil is maximum
  • At 63.2% of its maximum steady value
  • At the start of the current flow
  • After one time constant
  • Near the final maximum value of current
Q.5
Conductivity is analogous to
  • Retentivity
  • Resistivity
  • Permeability
  • Inductance
Q.6
The property of a material which opposes the creation of magnetic flux in it is known as
  • Reluctivity
  • Magneto-motive force
  • Permeance
  • Reluctance
Q.7
Hysteresis loss least depends on
  • Volume of material
  • Frequency
  • Steinmetz’s coefficient of material
  • Ambient temperature
Q.8
The unit of reluctance is
  • Meter/Henry
  • Henry/meter
  • Henry
  • 1/Henry
Q.9
Hard steel is suitable for making permanent magnets because
  • It has good residual magnetism
  • Its hysteresis loop has large area
  • Its mechanical strength is high
  • Its mechanical strength is low
Q.10
Energy stored by a coil is doubled when its current is increased by percent.
  • 25
  • 50.14
  • 41.4
  • 100
Q.11
The relative permeability of a ferromagnetic material is
  • Less than one
  • More than one
  • More than 10
  • More than 100 Ωr 1000
Q.12
The unit of retentivity is
  • Weber
  • Weber/sq. m
  • Ampere turn/meter
  • Ampere turns
Q.13
If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be
  • Zero
  • Small
  • Large
  • None of the above
Q.14
When both the inductance and resistance of a coil are doubled the value of
  • Time constant remains unchanged
  • Initial rate of rise of current is doubled
  • Final steady current is doubled
  • Time constant is halved
Q.15
Conductance is analogous to
  • Permeance
  • Reluctance
  • Flux
  • Inductance
Q.16
A ferrite core has less eddy current loss than an iron core because
  • Ferrites have high resistance
  • Ferrites are magnetic
  • Ferrites have low permeability
  • Ferrites have high hysteresis
Q.17
Permanent magnets are normally made of
  • Alnico alloys
  • Aluminium
  • Cast iron
  • Wrought iron
Q.18
Reciprocal of reluctance is
  • Reluctivity
  • Permeance
  • Permeability
  • Susceptibility
Q.19
Permeability in a magnetic circuit corresponds to_________ in an electric circuit.
  • Resistance
  • Resistivity
  • Conductivity
  • Conductance
Q.20
In a magnetic material hysteresis loss takes place primarily due to
  • Rapid reversals of its magnetization
  • Flux density lagging behind magnetizing force
  • Molecular friction
  • It high retentivity
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