The temperature coefficient of resistance of conductors is
positive
zero
negative
infinite
Correct Answer :
A. positive
Related Questions
A 200-watt lamp working for 24 hours will consume approximately _____ units.
When the current flowsa the magnetic field ��. conductor is in what direction?
The same as the current direction
Opposite the current direction
Omnidirectional
In the direction determined by the left hand rule
The unit of flux is _____ in cgs system.
Tesia
Gilbert
Maxwell
Oersted
What is the reluctance of a magnetic path having a length of 2x 10^-3m and crosssectional area of 2.5 x 10^-3 m^2?
6366 A, t/Wb
6000 A, t/Wb
8x10^-3 A, t/Wb
0.8 A, t/Wb
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 force between two magnetic poles is _______ their pole strengths.
directly proportional to
the sum of
inversely proportional to
the product of
Which of the following statements is TRUE?
Silicon dioxide is a good
The current carriers in conductors are valence electrons
For conductorsa the valence electron are strongly attracted to the nucleus
The valence electrons are located in the nucleus of an atom
What is the SI unit of conductance?
Siemens
Mhos
Ohms
1/Ohms
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
A t/m is a unit of
Mmf
Emf
Reluctance
Magnetizing force
A commercial alloy of aluminum nickela and iron with cobalta copper and titanium added to produce about 12 grades.
Alnico
Brass
Aluminum
Constantan
Whenever a flux inking a coil or current changesa an emf is induced in it. This is known as
Joule's Law
Coulomb's Law
Faraday's first law of electromagnetic induction
Faraday's second law of electromagnetic induction
What is the other name for dielectric strength?
Breakdown voltage
Electric intensity
Potential gradient
Dielectric constant
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.
The ratio between the intensity of magnetization produced in a substance to the magnetizing force producing it
Magnetic Reluctivity
Magnetic Resistivity
Magnetic susceptibility
Magnetic conductivity
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
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 direction of force o a current carrying conductor placed in a m found by
Cork screw rule
Fleming's left hand rule
Fleming's right hand rule
using a compass
The property of magnetic materials of retaining magnetism after withdrawal of the magnetizing force is known as
Retentivity
Reluctivity
Resistivity
Conductivity
What solid has no defined crystal structure except perhaps in the arrangement of the nearest neighboring atoms or ions?
Crystalline
Amorphous
Polycrystalline
Poly amorphous
What is used as the dielectric material in high voltage transformers?
Mica
Paraffin
Porcelain
Oiled paper
Hysteresis is a phenomenon of _________ in a magnetic circuit.
setting up constant flux
lagging of H behind B
lagging B behind H
leading B ahead H
At/m is a unit of
mmf
magnetic force
reluctance
magnetic flux density
How many neutrons does a copper atom have?
What is used as the insulating material or dielectric in an electric ion
Oiled paper
Mica
Paraffin
Tit anate compound
The magnetic field of a bar magnet most closely resembles the magnetic field of
a horseshoe magnet
a straight current- carrying wire
a stream of electrons moving parallel to one another
a current- carrying wire loop
When the relative permeability of a material is slightly more than 1a it is called ______ material.
diamagnetic
ferromagnetic
paramagnetic
non-magnetic
When a current carrying conductor is placed in a magnetic fielda the maximum force will act on the conductor when the conductor is at an angle of _______ to the magnetic field.
45o
60o
30o
90o
Lenz's law is the consequence of the law of conservation of
Energy
Charge
Field lines
Momentum
Germanium atom has ______ protons and ______ electrons.
32, 32
32, 42
42, 32
34, 34