What is the unit of magnetomotive force?
Volt
Tesla
Ampere- turn
Weber
Correct Answer :
C. Ampere- turn
Related Questions
The emf induced in a coil due to the change of its own flux linked with it is called
Mutually induced emf
Dynamically induced emf
Statically induced emf
Self induced emf
The ratio of the permeability of material to the permiabiity of air or vacuum.
Relative permeability
Relative permittivity
Relative conductivity
Relative reluctivity
The electric flux density is a ________ quantity.
phasor
vector
scalar
variable
The force between two magnetic poles is _____ the relative permeability of the medium.
directly proportional to
independent of
inversely proportional to
equal to
The force between two magnetic poles is _____ their poles strength.
equal to
directly proportional to
inversely proportional to
directly proportional to the square root of
Small voltages generated by a conductor with current in an external magnetic field.
Skin effect
Magnetic effect
Hall effect
Flywheel Effect
Magnetic effects of the earth as a huge magnet with north and south poles.
Diamagnetic
Ferromagnetic
Terrestrial magnetism
Terrestrial ferromagnetism
The induced emf in a wire loop that is moved parallel to a uniform magnetic field is
Zero
Dependent on the area of the loop
Dependent on the shape of the loop
Dependent on the magnitude of the field
The unit of flux density is
Wb/m
Tesla
At/m
N/Wb
What is the usual value of leakage coefficient for electrical machines?
0.5 to 1
1 to 5
5 to 10
1.15 to 1.25
The permittivity of a material is given by one of the following formulas.
DE
E/D
D^2/E
D/E
There are how many compounds available in nature?
300a000
Unlimited
How many neutrons does a copper atom have?
In electro-mechanical conversion devices like generators and motors the reason why a small air gap is left between the rotor and stator is to
permit mechanical clearance
increase flux density in air gap
decrease the reluctance of magnetic path
complete the magnetic path
Define as that pole which when placed in air from a similar and equal pole repels it with a force of newtons
North pole
South pole
Unit pole
Magnetic pole
The B-H curve of ________ is not a straight line.
air
wood
silicon steel
soft iron
At/m is a unit of
mmf
magnetic force
reluctance
magnetic flux density
Electric lines of force leave or enter the charge surface at an angle of
30o
45 o
90o
depending upon the angle of launch and entry
The conduction of electricity across the surface of a dielectric is called
creepage
skin effect
surface effect
crosstalk
The force between two charges placed a given distance apart ______ as the relative permittivity of the medium is increased.
increases
decreases
remains unchanged
becomes infinite
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
Whenever a conductor cuts magnetic fluxa an emf is induced in it. This is known as
Coulomb's law
Joule's law
Faraday's law
Ohm's law
Defined as the ratio of the volume occupied by the atoms or ions in a unit cell divided by the volume of the unit cell and is used to measure the compactness of a crystal.
Atomic packing factor (APF)
Ionic Packing Ratio (IPR)
Atomic compacting factor (ACF)
Ionic compacting ratio (ICR)
What is the main advantage of temporary magnets?
The magnetic flux can be changed.
Hysteresis can be decreased.
Magnetic materials can be used.
Abundance of ferromagnetic material that can be temporarily magnetized.
The temperature coefficient of resistance of conductors is
positive
zero
negative
infinite
When the current flowsa the magnetic field ��. conductor is in what direction?
The same as the current direction
Opposite the current direction
Omnidirectional
In the direction determined by the left hand rule
An alloy of 22 percent iron and 78 per cent nickel.
Permalloy
Alnico
Constantan
M anganin
A 200-watt lamp working for 24 hours will consume approximately _____ units.
Which of the following has the highest permeability?
Soft iron
Steel
Air
Permalloy
If the number of valence electrons of an atom is exactly 4a then the substance is called
a semiconductor
a conductor
an insulator
a cryogenic conductor