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.
Correct Answer :
A. The magnetic flux can be changed.
Related Questions
The reluctance of a magnetic circuit varies with
length × area
area � length
length � area
length + area
The total number of magnetic lines of force in a magnetic field is called
Magnetic flux
Magnetic flux density
Magnetic flux intensity
Magnetic potential
A magnetizing force of 1000 AT/m will produce a flux density of __________ i
1.257 mWb/m^2
0.63 Wb/m^2
1.257 Wb/m^2
0.63 mWb/m^2
Defined as the number of lines per unit area through any substance in a plane at right angles to the lines of force
Flux
Flux lines
Flux density
Flux intensity
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
The core of a magnetic equipment uses a magnetic material with
Least permeability
Low permeability
Moderate permeability
High permeability
When the relative permeability of a material is slightly more than 1a it is called ______ material.
diamagnetic
ferromagnetic
paramagnetic
non-magnetic
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
Materials whose permeabilities are slightly greater than that of free space
Paramagnetic
Non- magnetic
Ferromagnetic
Diamagnetic
The process by which an emf and hence current is generated or induced in a conductor when there is a change in the magnetic flux linking the conductor is called
Electromagnetic induction
Mutual induction
Faraday's law
Electromagnetic interference
A good conductor has how many valence electrons?
Used to maintain strength of magnetic field
Container
Air gap
Keeper
S ource
The force of attraction or repulsion between two magnetic poles is inversely proportional to the square of the distance between them. This is known as
Newton's first law
Faraday's first law of electromagnetic induction
Coulomb's first law
Coulomb's second law
Refers to the magnetic lines
Flux
Hysteresis
Current
Magnetomotive force
The force of attraction or repulsion between two magnetic poles is directly proportional to their strengths.
Newton's first law
Faraday's first law of electromagnetic induction
Coulomb's first law
Coulomb's second law
A positively charged body has
deficit of electrons
excess of neutrons
excess of electrons
deficit of protons
If the value of 25 of a conductor is 1/230 per oCa then the value of 0is
1/180 peroC
1/150 per oC
1/280 per oC
1/230 per oC
The net electrical charge in an isolated system remains constant. This is known as
Law of conservation of charge
Coulomb's first law
Coulomb's second law
Law of conservation of energy
How is mutual inductance between two coils decreased?
By using a common core
By moving the coils closer
By moving the coils apart
By increasing the number of turns of either coil
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
The emission of electrons from hot bodies is called
Radiation effect
Edison effect
Skin effect
Half effect
The electric potential across part AB of a circuit is 5 V; point A being at higher potential. If a charge of 5 Cmoves from A to Ba then energy released as
5 joules
25 joules
10 joules
100 joules
The force which set ups or tends to set up magnetic flux in a magnetic circuit
Dynamic force
Electromotive force
Potential difference
Magnetomotive force
The reluctance of the magnetic circuit is ________ relative permeability of the material comprising the circuit.
directly proportional to
inversely proportional to
independent of
dependent of
Mmf in a magnetic circuit corresponds to _____ in an electric circuit
Emf
Voltage drop
Electric Field Intensity
Potential gradient
Referred to as the specific reluctance of a material
Resistivity
Reluctivity
Conductivity
Permeability
Defined as a closed path in which magnetic induction or flux flows
Electric circuit
Magnetic circuit
Electronic circuit
Electromagnetic circuit
Who demonstrated the theory of electromagnetic induction in 1831?
Michael Faraday
Andre Ampere
James Clerk Maxwell
Charles Coulomb
Germanium atom has ______ protons and ______ electrons.
32, 32
32, 42
42, 32
34, 34
The property of magnetic materials of retaining magnetism after withdrawal of the magnetizing force is known as
Retentivity
Reluctivity
Resistivity
Conductivity