The temperature coefficient of resistance of insulators is
zero
negative
positive
infinite
Correct Answer :
B. negative
Related Questions
Magnetic fields do not interact with
Moving permanent magnets
Stationary permanent magnets
Moving electric charges
Stationary electric charges
Two similar polesa each 1Wba placed 1 m apart in air will experience a repulsive force of
63000 N
63 × 10^-3 N
8 × 10^12 N
796 kN
If the number of valence electrons of an atom is more than 4a the substance is called
a semiconductor
a conductor
an insulator
a semi-insulator
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
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 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
A factor used to correct for the electrostatic forces of the more distant ions in an ionic solid.
Avogadro's number
Planck's constant
Boltzmann's constant
Madelung constant
Who developed the electromagnetic theory of light in 1862?
Heinrich Rudolf Hertz
Wilhelm Rontgen
James Clerk Maxwell
Andre Ampere
Who discovered that a current-carrying conductor would move when placed in a magnetic field?
Michael Faraday
Andre Ampere
Hans Christian Oersted
Gustav Robert Kirchhoff
Flux linkages equals
Flux times area of core
Flux times number of turns times area of core
Flux times number of turns times length of core
Flux times number of turns
Referred to as the specific reluctance of a material
Resistivity
Reluctivity
Conductivity
Permeability
Refers to the magnetic lines
Flux
Hysteresis
Current
Magnetomotive force
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
Permanent magnets can be found in
electric bells
earphones
relays
dy namic loudspeakers
One of the common application of an air- cored choke.
Radio frequency
Audio frequency
Power supply
Power transformer
A negative ion results when an atom gains an additional
Electron
Proton
Neutron
Atom
Who demonstrated the theory of electromagnetic induction in 1831?
Michael Faraday
Andre Ampere
James Clerk Maxwell
Charles Coulomb
The uncharged particles which have no effect on its atomic charge.
Nucleons
Electrons
Protons
Neutrons
Electric field intensity is a ________.
scalar
phasor
vector
variable
There are how many compounds available in nature?
300a000
Unlimited
Core materials of a good relay have _________ hysteresis loop.
large
narrow
very large
very narrow
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
The temperature coefficient of resistance of insulators is
zero
negative
positive
infinite
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
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
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
Define as that pole which when placed in air from a similar and equal pole repels it with a force of newtons
North pole
South pole
Unit pole
Magnetic pole
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 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 unit of flux density is
Wb/m
Tesla
At/m
N/Wb