A permanent magnet does not exert a force on
an unmagnetized iron bar
a magnetized iron bar
a moving electric charge
a stationary electric charge
Correct Answer :
D. a stationary electric charge
Related Questions
The potential at a point due to a charge is 15 V. If the distance is times, the potential at the point will be
5 V
18 V
45 V
15 V
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 permittivity of a material is given by one of the following formulas.
DE
E/D
D^2/E
D/E
What is the SI unit of conductivity?
Ohms/m
Ohms-m
Siemens-m
Siemens/m
One of the common application of an air- cored choke.
Radio frequency
Audio frequency
Power supply
Power transformer
Calculate the permeability (in T/A. t/m) of a magnetic material that has a relative permeability of 300
3.78 x 10^4
3.78 x 10^-5
3.78 x 10^-3
3.78 x 10^-6
______ is an electromagnet with its core in the form of a close magnetic ring.
S olenoid
Paraboloid
Toroid
Cycloid
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
If the relative permittivity of a material is 10a then its permittivity is
4 × 10^7F/m
4 × 10^-6 F/m
8.854× 10^-11 F/m
8.854 × 10^-12 F/m
Hysteresis refers to the ______ between flux density of the material and the magnetizing force applied.
Leading effect
Ratio
Equality
Lagging effect
The electric flux density is a ________ quantity.
phasor
vector
scalar
variable
Flux density is measured in
Tesia
Weber
Ampere- turn
Maxwell
Defined as a closed path in which magnetic induction or flux flows
Electric circuit
Magnetic circuit
Electronic circuit
Electromagnetic circuit
A 6- V battery is connected across a solenoid of 100 turns having a resistance of 2 ?a Calculate the number of ampere turns?
If the number of valence electrons of an atom is less than 4a the substance is called
a conductor
a semiconductor
an insulator
a superconductor
A substance that attracts pieces iron
Conductor
Semiconductor
Magnet
All of the above
What is the practical unit of electrical energy?
Watt
Kilowatt-hour
Kilowatt-second
Megawathour
A negative ion results when an atom gains an additional
Electron
Proton
Neutron
Atom
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
How much is the flux in Weber in the above problem?
2 x 10^-5
2 x 10^-3
2 x 10^5
2 x 10^3
Magnetic field intensity is a ________ quantity.
scalar
phasor
vector
variable
The B-H curve for ________ is a straight line passing through the origin.
cobalt
air
hardened steel
soft iron
The branch of Engineering which deals with the magnetic effect of electric current is known as
Magnetism
Electromagnetism
Electrical engineering
Electronics engineering
Cobalt is an example of a ______ material.
Paramagnetic
Diamagnetic
Ferromagnetic
Non- magnetic
When the ferromagnetic substance is inserted in a current- carrying solenoida the magnetic field is
Greatly decreased
Greatly increased
Slightly decreased
Slightly increased
What is another name for relative permittivity?
Dielectric strength
Electric intensity
Potential gradient
Dielectric constant
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 temperature coefficient of resistance of semiconductors is
positive
zero
negative
infinite
Which of the following materials has the least hysteresis loop area?
soft iron
silicon steel
hard steel
wrought iron
Back emf refers to the
Current equal to the applied emf
Opposing emf
Current opposing the applied emf
Voltage opposing the applied emf