Which of the following is used by temporary magnets as the magnetic material?
Hardened steel
Cobalt steel
Soft iron
Tungsten steel
Correct Answer :
C. Soft iron
Related Questions
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
The air space between poles of magnets
Air gap
Free space
Vacuum
Atmosphere
Small voltages generated by a conductor with current in an external magnetic field.
Skin effect
Magnetic effect
Hall effect
Flywheel Effect
Who developed the electromagnetic theory of light in 1862?
Heinrich Rudolf Hertz
Wilhelm Rontgen
James Clerk Maxwell
Andre Ampere
A law that states that the current in a thermionic diode varies directly with the three- halves power of anode voltage and inversely with the square of the distance between the electrodesa provided operating conditions are such that the current is limited only by the space charge.
Hall's law
Joule's law
Child's law
Coulomb's law
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
Lenz's law is the consequence of the law of conservation of
Energy
Charge
Field lines
Momentum
The current of electric circuit is analogous to which quantity of a m
Mmf
Flux
Flux density
R eluctivity
The relative permeability of a magnetic material is 10^5. What is its permeability?
4 × 10^5 H/m
4 × 10^-12 H/m
4× 10^-2 H/m
4 × 10^7H/m
A commercial alloy of aluminum nickela and iron with cobalta copper and titanium added to produce about 12 grades.
Alnico
Brass
Aluminum
Constantan
A group of magnetically aligned atoms is called
Range
Lattice
Domain
Crystal
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
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
The force between two magnetic poles varies with the distance between them. The variation is ______ to the square of that distance.
Equal
Greater than
Directly proportional
Inversely proportional
Who demonstrated that there are magnetic effects around every current-carrying conductor and that current-carrying conductors can attract and repel each other just like magnets?
Luigi Galvani
Hans Christian Oersted
Charles Coulomb
Andre Ampere
Electron is a Greek word for
amber
Fire
Stone
Heat
Materials whose permeabilities are slightly greater than that of free space
Paramagnetic
Non- magnetic
Ferromagnetic
Diamagnetic
Electromotive force in a circuit
causes free electrons to flow
increases the circuit resistance
maintains circuit resistance
is needed to make the circuit complete
One weber of flux is equal to _______ magnetic lines of force.
10^6
10^10
4 × 10^7
10^8
If the number of valence electrons of an atom is less than 4a then the substance is probably
a metal
an insulator
a non-metal
a semiconductor
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
When a conductor is stationary and the magnetic field is moving or changing the emf induced is called
Statically induced emf
Mutually induced emf
Self induced emf
Dynamically induced emf
The space outside the magnet where its pole have a force of attraction or repulsion on a magnetic pole is called
Magnetic field
Electric field
Electromagnetic field
Free Space Field
Back emf refers to the
Current equal to the applied emf
Opposing emf
Current opposing the applied emf
Voltage opposing the applied emf
Defined as a closed path in which magnetic induction or flux flows
Electric circuit
Magnetic circuit
Electronic circuit
Electromagnetic circuit
Magnetic effects of the earth as a huge magnet with north and south poles.
Diamagnetic
Ferromagnetic
Terrestrial magnetism
Terrestrial ferromagnetism
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
Permeability means
The conductivity of the material for magnetic lines of force
The magnetization test in the material after exciting field has been removed
The strength of an electromagnet
The strength of the permanent magnet
When the relative permeability of a material is much greater than 1a it is called _______ material.
diamagnetic
ferromagnetic
paramagnetic
non-magnetic
If the right handed bottle-opener cork screw is assumed to be along the conductor so as to advance in the direction of current flow, the motion of its handle will indicate the direction of magnetic flux produced around the conductor. This is known as
Right hand rule
Left hand rule
Cork screw rule
End rule