States that the ratio of the thermal conductivity is proportional to the absolute temperature for all metals.
Wien's displacement law
Hartleys law
Hall's law
Wiedemann Franz law
Correct Answer :
D. Wiedemann Franz law
Related Questions
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
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
What is the SI unit of specific resistance or resistivity?
Ohm-circular mil per inch
Ohm-circular mil per foot
Ohm-m
Ohm-cm
When the relative permeability of a material is much greater than 1a it is called _______ material.
diamagnetic
ferromagnetic
paramagnetic
non-magnetic
The air space between poles of magnets
Air gap
Free space
Vacuum
Atmosphere
The permeability of a material having a flux density of 5 Wb/m^2 is 10^-5 H/m. What is the value of magnetizing force?
5 × 10^-5 N/Wb
500 × 10^3 N/Wb
4 × 10^7N/Wb
4 × 10^7N/Wb
If on looking at any one end of a solenoid; the direction of current flow is found to be clockwise then the end under observation is a south pole. This is known as
Right hand rule
Left hand rule
Cork screw rule
End Rule
The greater percentage of materials is _________.
diamagnetic
paramagnetic
ferromagnetic
non-magnetic
Which of the following materials has the least hysteresis loop area?
soft iron
silicon steel
hard steel
wrought iron
The ratio of the permeability of material to the permiabiity of air or vacuum.
Relative permeability
Relative permittivity
Relative conductivity
Relative reluctivity
Which of the following is used by temporary magnets as the magnetic material?
Hardened steel
Cobalt steel
Soft iron
Tungsten steel
An alloy of 22 percent iron and 78 per cent nickel.
Permalloy
Alnico
Constantan
M anganin
The B-H curve of ________ is not a straight line.
air
wood
silicon steel
soft iron
Which of the following electric quantities is vector in character?
Field
Charge
Energy
Potential Difference
The phenomenon by which a magnetic substance becomes a magnet when it is place near a magnet
Magnetic effect
Magnetic phenomenon
Magnetic induction
Electromagnetic induction
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
If a 20 V potential is applied across a relay coil with 50 turns having 1 ? of resistancea the total magnetomotive producing magnetic flux in the circuit is
10 Wb
50 T
1000 A t/m
1000,t
The energy stored in an electrostatic field or electromagnetic field is called
Electromagnetic energy
Kinetic energy
Potential energy
R est energy
Amorphous solid is also called
Crystalline
Non- crystalline
Polycrystalline
Homogenous
The magnetic flux through a coil changes. This results to the induced emf acting in a direction as to
Oppose the change
Aid the change
Either oppose or aid the change
Neither oppose nor aid the change
The conduction of electricity across the surface of a dielectric is called
creepage
skin effect
surface effect
crosstalk
Who discovered superconductivity in 1911?
Kamerlingh Onnes
Alex Muller
GeoryBednorz
Charles Coulomb
The contribution to the ionization in an ionization chamber by electrons liberated from t he walls.
Skin effect
Walt effect
Hall effect
Edison effect
Hysteresis refers to the ______ between flux density of the material and the magnetizing force applied.
Leading effect
Ratio
Equality
Lagging effect
What is the SI unit of conductance?
Siemens
Mhos
Ohms
1/Ohms
A principle that states that only two electrons with different spins are allowed to exist in a given orbit
Bohr's principle
Pauli exclusion principle
Avogadro's principle
Coulomb's principle
If a magnetic flux cuts across 200 turns at a rate of 2Wb/sa the induced voltage according to Faraday's law is about
400 V
100 V
200 V
600 V
The current of electric circuit is analogous to which quantity of a m
Mmf
Flux
Flux density
R eluctivity
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
What is the relative permittivity of air?
8.854 × 10^-12
4 × 10^7