Residual magnetism refers to the flux densitya which exists in the iron core when the magnetic field intensity is
Minimized
Reduced to zero
Maximize
Unity
Correct Answer :
B. Reduced to zero
Related Questions
If you hold the conductor with right hand so that the stretched thumb points in the direction of the currenta then encircling fingers will give the direction of magnetic lines of force round the conductor. This is known as
Left hand cork screw rule
Right hand cork screw rule
Left hand rule
Right hand rule
Bonding of atoms that is due to the force of attraction between positive ions and a group of negative ions
Ionic bond
Covalent Bond
Electrostatic Bond
Metallic bond
Temporary magnets are commonly employed in
electric instruments
motors
moving coils loudspeakers
magnetos
Electric field intensity at a point due to a given charge ______ if the relative permittivity of the medium decreases.
decreases
remains unchanged
increases
b ecomes zero
Three charges of +5 Ca -6 C and +9 C are placed inside a sphere. What is the total flux passing through the surface of sphere?
8 C
14 C
20 C
-6 C
Electromotive force in a circuit
causes free electrons to flow
increases the circuit resistance
maintains circuit resistance
is needed to make the circuit complete
The magnetic flux through a wire loop in a magnetic field does not d
T he area of the loop
The magnitude of the field
The shape of the loop
The angle between the plane of the loop and the direction
Magnetic field intensity is a ________ quantity.
scalar
phasor
vector
variable
A magnetic circuit carries a flux iin the iron part and a fluxgin the air gap. What is the leakage coefficient?
i/g
i × g
g/ i
i + g
The unit of flux density is
Wb/m
Tesla
At/m
N/Wb
Electric field intensity at a point is numerically equal to ________ at that point.
potential gradient
potential difference
dielectric constant
the force
The force between two magnetic poles is _______ their pole strengths.
directly proportional to
the sum of
inversely proportional to
the product of
The branch of Engineering which deals with the magnetic effect of electric current is known as
Magnetism
Electromagnetism
Electrical engineering
Electronics engineering
A theorem which states that an electric current flowing in a circuit produces a magnetic field at external points equivalent to that due to a magnetic shell whose bounding edge is the conductor and whose strength of the current.
Joule's law
Faraday's law
Volta's theorem
Ampere's theorem
An electron- volt (eV) is a unit of
Energy
Potential difference
Charge
Momentum
Which of the following statements is TRUE?
Silicon dioxide is a good
The current carriers in conductors are valence electrons
For conductorsa the valence electron are strongly attracted to the nucleus
The valence electrons are located in the nucleus of an atom
The core of a transformer heats up when its primary is fed from an ac source because of
permeability
ferromagnetism
reluctance of core
hysteresis loss
What is the SI unit of conductance?
Siemens
Mhos
Ohms
1/Ohms
A magnetic material losses its ferromagnetic properties at a point called
Curie temperature
Inferred absolute temperature
Room temperature
Absolute temperature
One of the common application of an air- cored choke.
Radio frequency
Audio frequency
Power supply
Power transformer
Which of the following is a paramagnetic material?
Carbon
Copper
Bismuth
Oxygen
What is the relative permittivity of air?
8.854 × 10^-12
4 × 10^7
The magnetic materials should have a large hysteresis loss for one of the following applications.
Transformers
ACmotors
Permanent Magnets
DC generators
What is the SI unit of conductivity?
Ohms/m
Ohms-m
Siemens-m
Siemens/m
The electric potential at a point in air due to a charge is 21 V. If the air is replaced by a medium of relative permittivity of 3a then electric potential at that point will be
63 V
21 V
7 V
42 V
Two similar polesa each 1Wba placed 1 m apart in air will experience a repulsive force of
63000 N
63 × 10^-3 N
8 × 10^12 N
796 kN
When a wire loop is rotated in a magnetic field the direction of the induced emf changes one in every _______ revolution
If the value of 0 a conductor is 1/234 per oCa then the value of 18is
1/218 per oC
1/252 peroC
1/272 per oC
1/273 per oC
An alloy of 22 percent iron and 78 per cent nickel.
Permalloy
Alnico
Constantan
M anganin
One ampere- turn is equivalent to _____ gilberts