Theory of ferromagnetic phenomena which assumes each atom is a permanent magnet which can turn freely about its center under the influence of applied field and other magnets.
Ewing's theory of ferromagnetism
Oersted's ferromagnetism theory
Maxwell's magnetic theory
Ampere's circuital law
Correct Answer :
A. Ewing's theory of ferromagnetism
Related Questions
An alloy of 22 percent iron and 78 per cent nickel.
Permalloy
Alnico
Constantan
M anganin
The contribution to the ionization in an ionization chamber by electrons liberated from t he walls.
Skin effect
Walt effect
Hall effect
Edison effect
Steel is hard to magnetize because of its
Low permeability
High permeability
High density
High retentivity
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
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
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
The ratio of the permeability of material to the permiabiity of air or vacuum.
Relative permeability
Relative permittivity
Relative conductivity
Relative reluctivity
A one cubic cm of copper has how many free electrons at room temperature?
80 × 10^18
8.5 × 10^22
20 × 10^10
50 × 10^20
Which of the following materials has the least hysteresis loop area?
soft iron
silicon steel
hard steel
wrought iron
One electron volt (1 eV) is equivalent to _____ joules
1.3 x 10^-19
1.4 x 10^-19
1.5 x 10^-19
1.6 x 10^-19
The current of electric circuit is analogous to which quantity of a m
Mmf
Flux
Flux density
R eluctivity
Electric field intensity is a ________.
scalar
phasor
vector
variable
Refers to the non- metallic materials that have the ferromagnetic properties of iron.
Ferrites
Ferromagnetic
Diamagnetic
Paramagnetic
Which of the following is a natural magnet?
Steel
Magnesia
Lodestone
S oft iron
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
The physical motion resulting from the forces of magnetic fields is called
Motor action
Rotation
Repulsion
Torque action
The phenomenon that when an electric current passes through an anisotropic crystala there is an absorption or liberation of heat due to the non-uniformity in current distribution.
Bridgman effect
Corona effect
Dember effect
Destriau effect
The science of adapting electronics to aerospace flight.
Avionics
Aerotronics
Aerodynamics
Astrionics
The resistivity of a conductor ___________ with an increase in temperature.
increases
decreases
remains the same
becomes zero
The emf produced in a wire by its motion across a magnetic field does not depend upon the
Diameter of the wire
Length of the wire
Orientation of the wire
Flux density of the field
The uncharged particles which have no effect on its atomic charge.
Nucleons
Electrons
Protons
Neutrons
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
__________ is a substance of whose molecules consist of the same kind of atom.
Mixture
Compound
Element
Isotope
Who discovered superconductivity in 1911?
Kamerlingh Onnes
Alex Muller
GeoryBednorz
Charles Coulomb
Back emf refers to the
Current equal to the applied emf
Opposing emf
Current opposing the applied emf
Voltage opposing the applied emf
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
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
The emission of electrons from hot bodies is called
Radiation effect
Edison effect
Skin effect
Half effect
If two similar charges 1 coulomb each are placed 1 m apart in aira then the force of repulsion is
8 × 10^6 N
9 × 10 ^9 N
10^6 N
5 × 10^6 N
Lenz' law states that the direction of the induced emf and hence current
Is determined by the rate of current flux
Is found by the right hand rule
Is found by the left hand rule
Always opposes the cause producing it