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
Correct Answer :
B. The current carriers in conductors are valence electrons
Related Questions
What solid has no defined crystal structure except perhaps in the arrangement of the nearest neighboring atoms or ions?
Crystalline
Amorphous
Polycrystalline
Poly amorphous
The magnetic field inside a solenoid
is zero
is uniform
increases with distance from the axis
decreases with distance from the axis
The permittivity of a material is given by one of the following formulas.
DE
E/D
D^2/E
D/E
What bond is formed when one or more electrons in the outermost energy orbit of an atom are transferred to another?
Ionic
Covalent
Metallic
Van der Waals
The resistivity of a conductor ___________ with an increase in temperature.
increases
decreases
remains the same
becomes zero
The straight line passing through the two poles of magnet is called
Real axis
Cartesian axis
Magnetic axis
Imaginary axis
If the magnetic material is located within a coil through which alternating current (60 Hz frequency) flowsa then __________ hysteresis loops will be formed
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
A magnetic flux of 2.5 x10^4 Wb through an area of 5 x10^4 square meters results in
5 Wb
0.5 Tesia of flux density
5x 10^-5 Wb of flux
5000 Tesia of flux density
Referred to as the specific reluctance of a material
Resistivity
Reluctivity
Conductivity
Permeability
The flux density in an air-cored coil is 10^-3 Wb/m^2. With a cast iron core of relative permeability 100 inserteda the flux density will become
10^-3 Wb/m^2
10^-2 Wb/m^2
10^3 Wb/m^2
0.1 Wb/m^2
A theorem which states that an electric current flowing in a circuit produces a magnetic field at external points equivalent to that due to a magnetic shell whose bounding edge is the conductor and whose strength of the current.
Joule's law
Faraday's law
Volta's theorem
Ampere's theorem
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
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
The physical motion resulting from the forces of magnetic fields is called
Motor action
Rotation
Repulsion
Torque action
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
The core of a magnetic equipment uses a magnetic material with
Least permeability
Low permeability
Moderate permeability
High permeability
Refers to the magnetic lines
Flux
Hysteresis
Current
Magnetomotive force
Whenever a conductor cuts magnetic fluxa an emf is induced in it. This is known as
Coulomb's law
Joule's law
Faraday's law
Ohm's law
Which of the following has the least number of valence electrons?
Conductor
Semiconductor
Insulator
Semi- insulator
Which of the following is used by temporary magnets as the magnetic material?
Hardened steel
Cobalt steel
Soft iron
Tungsten steel
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
The core of a transformer heats up when its primary is fed from an ac source because of
permeability
ferromagnetism
reluctance of core
hysteresis loss
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
The relation between absolute permittivity of air ( 0)a absolute p and velocity of light (c) is given by
0 0= c^2
0 0= c
1/ 0 0= c
1/ 0 0= c^2
The hot resistance of an incandescent lamp is about _______ its cold resistance.
10 times
100 times
5 times
50 times
Flux density is measured in
Tesia
Weber
Ampere- turn
Maxwell
Core materials of a good relay have _________ hysteresis loop.
large
narrow
very large
very narrow
The electric flux density is a ________ quantity.
phasor
vector
scalar
variable
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