Q.1
An open coil has
Q.2
The self inductances of two coils are 8 mH and 18 mH. If the coefficient of coupling is 0.5, the mutual inductance of the coils is
Q.3
Reversing the field or the current will reverse the force on the conductor.
Q.4
The coefficient of coupling between two air core coils depends on
  • Self-inductance of two coils only
  • Mutual inductance between two coils only
  • Mutual inductance and self inductance of two coils
  • None of the above
Q.5
The law that the induced e.m.f. and current always oppose the cause producing them is due to
  • Faraday
  • Lenz
  • Newton
  • Coulomb
Q.6
The core of a coil has a length ofmm. The inductance of coil is 6 mH. If the core length is doubled, all other quantities, remaining the same, the inductance will be
  • 3 mH
  • 12 mH
  • 24 mH
  • 48 mH
Q.7
Mutually inductance between two magnetically coupled coils depends on
  • Permeability of the core
  • The number of their turns
  • Cross-sectional area of their common core
  • All of the above
Q.8
Lenz's law is a consequence of the law of conservation of
  • Induced current
  • Charge
  • Energy
  • Induced e.m.f.
Q.9
A crack in the magnetic path of an inductor will result in
  • Unchanged inductance
  • Increased inductance
  • Zero inductance
  • Reduced inductance
Q.10
A conductor carriesamperes of current underto a magnetic field of 1.1 tesla. The force on the conductor will be nearly
  • 50 N
  • 120 N
  • 240 N
  • 480 N
Q.11
The magnitude of the induced e.m.f. in a conductor depends on the
  • Flux density of the magnetic field
  • Amount of flux cut
  • Amount of flux linkages
  • Rate of change of flux-linkages
Q.12
An average voltage ofV is induced in aturns solenoid as a result of a change in flux which occurs in 0.5 second. The total flux change is
  • 20 Wb
  • 2 Wb
  • 0.2 Wb
  • 0.02 Wb
Q.13
In case of an inductance, current is proportional to
  • Voltage across the inductance
  • Magnetic field
  • Both A and B
  • Neither A)nor B
Q.14
A laminated iron core has reduced eddy-current losses because
  • More wire can be used with less resistance in coil
  • The laminations are insulated from each other
  • The magnetic flux is concentrated in the air gap of the core
  • The laminations are stacked vertically
Q.15
The self-inductance of the coil may be defined as equal to the e.m.f. induced in volts when the current in the circuit changes at the rate of unit Weber turns.
  • Yes
  • No
Q.16
The inductance of a coil will increase under all the following conditions except
  • When more length for the same number of turns is provided
  • When the number of turns of the coil increase
  • When more area for each turn is provided
  • When permeability of the core increases
Q.17
As per Faraday's laws of electromagnetic induction, an e.m.f. is induced in a conductor whenever it
  • Lies perpendicular to the magnetic flux
  • Lies in a magnetic field
  • Cuts magnetic flux
  • Moves parallel to the direction of the magnetic field
Q.18
Air-core coils are practically free from
  • Hysteresis losses
  • Eddy current losses
  • Both A and B
  • None of the above
Q.19
Higher the self-inductance of a coil,
  • Lesser its weber-turns
  • Lower the e.m.f. induced
  • Greater the flux produced by it
  • Longer the delay in establishing steady current through it
Q.20
In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will
  • Increase
  • Decrease
  • Remain the same
  • Initially increase and then decrease
0 h : 0 m : 1 s