Q.1

A magnetic field is made up of flux lines.

  • True
  • False
Q.2

Hysteresis is the number of lines of force per unit area in a magnetic field.

  • True
  • False
Q.3

A relay is an electromagnetically controlled mechanical device in which electrical contacts are opened or closed by a magnetizing current.

  • True
  • False
Q.4

Reluctance in a magnetic circuit is analogous to current in an electrical circuit.

  • True
  • False
Q.5

If a conductor is moved back and forth at a constant rate in a constant magnetic field, the voltage in the conductor will reverse polarity.

  • True
  • False
Q.6

Materials with a low retentivity do not retain a magnetic field very well.

  • True
  • False
Q.7
A magnetic field exists around
  • iron
  • copper
  • aluminium
  • moving charges
Q.8
For a given wire-wound 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.9
Which of the following is expected to have the maximum permeability ?
  • Brass
  • Copper
  • Zinc
  • Ebonite
Q.10
The attraction capacity of electromagnet will increase if the
  • core length increases i
  • core area increases
  • flux density decreases
  • flux density increases
Q.11
Unit for quantity of electricity is
  • ampere-hour
  • watt
  • joule
  • coulomb
Q.12
The initial permeability of an iron rod is
  • the highest permeability of the iron rod
  • the lowest permeability of the iron rod
  • the permeability at the end of the iron rod
  • the permeability almost in non-magnetised state
Q.13
The working of a meter is based on the use of a permanent magnet. In order to protect the meter functioning from stray magnetic fields
  • meter is surrounded by strong magnetic fields
  • a soft iron shielding is used
  • a plastic shielding is provided
  • a shielding of anon-magnetic material is used
Q.14
Aturn coil having an axial length ofmm and a radius ofmm is pivoted in a magnetic field having a flux density of 0.8 T. If the coil carries a current of 0.5 A, the torque acting on the coil will be [Hint. Torque = 2BIlNr N-m]
  • 8 N-m
  • 0.48 N-m
  • 0.048 N-m
  • 0.0048 N-m
Q.15
The main constituent of permalloy is
  • cobalt
  • chromium
  • nickel
  • tungsten
Q.16
Tesla is a unit of
  • field strength
  • inductance
  • flux density
  • flux
Q.17
The bar magnet has
  • the dipole moment
  • monopole moment
  • (A) and (B) both
  • none of the above
Q.18
The electromagnet hasturns and a current offlows through the coil. If the length of the magnet circuit ismm, what is the magnetic field strength?
  • 2500 AT/m
  • 250 AT/m
  • 25 AT/m
  • 2.5 AT/m
Q.19
If a copper disc is rotated rapidly below a freely suspended magnetic needle, the magnetic needle shall start rotating with a velocity
  • less than that of disc but in opposite direction
  • equal to that of disc and in the same direction
  • equal to that of disc and in the opposite direction
  • less than that of disc and in the same direction
Q.20
The unit of relative permeability is
  • henry/metre
  • henry
  • henry/sq. m
  • it is dimensionless
Q.21
Out of the following statements, concerning an electric field, which statement is not true?
  • The electric intensity is a vector quantity
  • The electric field intensity at a point is numerically equal to the force exerted upon a charge placed at that point
  • An electric field is defined as a point in space at which an electric charge would experience a force
  • Unit field intensity in the exertion of a force of one newton on a charge of one coulomb
Q.22
The force between two long parallel conductors is inversely proportional to
  • Radius of conductors
  • Current in one conductor
  • Product of current in two conductors
  • Distance between the conductors
Q.23
Ferrites are a sub-group of
  • non-magnetic materials
  • ferro-magnetic materials
  • paramagnetic materials
  • ferri-magnetic materials
Q.24
Fleming's left hand rule is used to find
  • Direction of magnetic field due to current carrying conductor
  • Direction of flux in a solenoid
  • Direction of force on a current carrying conductor in a magnetic field
  • Polarity of a magnetic pole
Q.25
Core of an electromagnet should have
  • low coercivity
  • high susceptibility
  • both of the above
  • none of the above
Q.26
The uniform magnetic field is
  • the field of a set of parallel conductors
  • the field of a single conductor
  • the field in which all lines of magnetic flux are parallel and equidistant
  • none of the above
Q.27
Ferrites are materials.
  • paramagnetic
  • diamagnetic
  • ferromagnetic
  • none of the above
Q.28
The commonly used material for shielding or screening magnetism is
  • copper
  • aluminium
  • soft iron
  • brass
Q.29
The ratio of intensity of magnetisation to the magnetisation force is known as
  • flux density
  • susceptibility
  • relative permeability
  • none of the above
Q.30
What is the magnitude and the direction of force per 1.length of a pair of conductors of a direct current linecarryingamperes and spacedmm apart ?
  • 22 x 10"8 N
  • 22 x 10"7 N
  • 22 x 10-6 N
  • 22 x 10"5 N
0 h : 0 m : 1 s