Permanent magnets can be found in
electric bells
earphones
relays
dy namic loudspeakers
Correct Answer :
B. earphones
Related Questions
Magnetic intensity is a
Phasor quantity
Physical quantity
Scalar quantity
Vector quantity
All matters (gasa liquid and solid) are composed of
Neutrons
Particles
Electrons
Atoms
The direction of force o a current carrying conductor placed in a m found by
Cork screw rule
Fleming's left hand rule
Fleming's right hand rule
using a compass
One of the common application of an air- cored choke.
Radio frequency
Audio frequency
Power supply
Power transformer
Core materials of a good relay have _________ hysteresis loop.
large
narrow
very large
very narrow
__________ is a substance of whose molecules consist of the same kind of atom.
Mixture
Compound
Element
Isotope
Which of the following electric quantities is vector in character?
Field
Charge
Energy
Potential Difference
One oersted (Oe) is equivalent to _____ Gb/cm.
Which of the following materials has the highest dielectric strength?
Glass
Oiled paper
Mica
Air
The amount of magnetizing force to counter balance the resid magnetic material is referred to as
Reluctivity
Susceptivity
Coercivity
Retentivity
Hydrogen is an example of a _____ material.
Paramagnetic
Diamagnetic
Ferromagnetic
N on- magnetic
Cobalt is an example of a ______ material.
Paramagnetic
Diamagnetic
Ferromagnetic
Non- magnetic
What solid has no defined crystal structure except perhaps in the arrangement of the nearest neighboring atoms or ions?
Crystalline
Amorphous
Polycrystalline
Poly amorphous
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
Which of the following is used by temporary magnets as the magnetic material?
Hardened steel
Cobalt steel
Soft iron
Tungsten steel
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
Ohm's law can be used only to a _____ circuit or component.
Unilateral
Exponential
Trivalent
Linear
A magnetic field is
The current flow through space around a permanent magnet
The force set up when current flows through a conductor
The force that drives current through a resistor
The force between the plates of a charged capacitor
The science of adapting electronics to aerospace flight.
Avionics
Aerotronics
Aerodynamics
Astrionics
A current if flowing east along a power line. If the earth's field is neglecteda the direction of the magnetic field below it is
North
South
East
West
A substance that attracts pieces iron
Conductor
Semiconductor
Magnet
All of the above
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
What is the SI unit of conductivity?
Ohms/m
Ohms-m
Siemens-m
Siemens/m
If the resistance of a material 2 m long and 2 m^2 in area of cross-section is 1.6 ×10^-8 ?a then its resistivity is
3.2 × 10^-8 ?-m
1.6 × 10^-8 ?-m
0.64 × 10^-8 ?-m
0.16 × 10^-8 ?-m
The evaporation of electrons from a heated surface is called
Radiation
Convection
Thermionic emission
Conduction
At/m is a unit of
mmf
magnetic force
reluctance
magnetic flux density
Who demonstrated the theory of electromagnetic induction in 1831?
Michael Faraday
Andre Ampere
James Clerk Maxwell
Charles Coulomb
The reluctance of a magnetic circuit is not dependent on which of the following?
Number of turns of coil
Magnetomotive force
Flux density in the circuit
Current in the coil
What determines the value of the temperature coefficient of resistance of a material?
length
cross-sectional area
volume
nature and temperature
The emf induced in a coil due to the changing current of another neighboring coil is called
Mutually induced emf
Self induced emf
Statically induced emf
Dynamically induced emf