There are how many compounds available in nature?
300a000
Unlimited
Correct Answer :
D. Unlimited
Related Questions
Cobalt is an example of a ______ material.
Paramagnetic
Diamagnetic
Ferromagnetic
Non- magnetic
Referred to as the specific reluctance of a material
Resistivity
Reluctivity
Conductivity
Permeability
The electric potential at a point in air due to a charge is 21 V. If the air is replaced by a medium of relative permittivity of 3a then electric potential at that point will be
63 V
21 V
7 V
42 V
The quantity of magnetism retained by a magnetic material after withdrawal of the magnetizing force is called
Leftover magnetism
Hysteresis
Residual magnetism
Coercivity
Under ordinary conditionsa a body is considered
positively charged
neutral
negatively charged
stable
What is the value of the absolute permittivity of air?
8.854 F/m
8.854 × 10^-12 mF/m
8.854× 10^-12 F/m
8.854 × 10^-12 F/m
A good conductor has how many valence electrons?
Who demonstrated that there are magnetic effects around every current-carrying conductor and that current-carrying conductors can attract and repel each other just like magnets?
Luigi Galvani
Hans Christian Oersted
Charles Coulomb
Andre Ampere
The tiniest element of matter
Atom
Proton
Electron
Neutron
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
Which of the following materials has the highest dielectric strength?
Glass
Oiled paper
Mica
Air
The temperature coefficient of resistance of semiconductors is
positive
zero
negative
infinite
The magnitude of the induced emf in a coil is directly proportional to the rate of change of flux linkages. This is known as
Joule's Law
Faraday's second law of electromagnetic induction
Faraday's first law of electromagnetic induction
Coulomb's Law
A substance that attracts pieces iron
Conductor
Semiconductor
Magnet
All of the above
Which of the following has the highest permeability?
Soft iron
Steel
Air
Permalloy
The evaporation of electrons from a heated surface is called
Radiation
Convection
Thermionic emission
Conduction
Electric field intensity at a point is numerically equal to ________ at that point.
potential gradient
potential difference
dielectric constant
the force
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
A negatively charge body has
deficit of electrons
excess of protons
excess of electrons
deficit of neutrons
The straight line passing through the two poles of magnet is called
Real axis
Cartesian axis
Magnetic axis
Imaginary axis
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
If the number of valence electrons of an atom is exactly 4a then the substance is called
a semiconductor
a conductor
an insulator
a cryogenic conductor
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
The reluctance of a magnetic circuit varies with
length × area
area � length
length � area
length + area
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
What is another name for relative permittivity?
Dielectric strength
Electric intensity
Potential gradient
Dielectric constant
A law that states that the polarity of the induced voltage will oppose the change in magnetic flux causing the induction.
Joule's law
Faraday's law
Coulomb's law
Lenz' law
Which of the following materials has the least hysteresis loop area?
soft iron
silicon steel
hard steel
wrought iron
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
Materials whose permeabilities are slightly greater than that of free space
Paramagnetic
Non- magnetic
Ferromagnetic
Diamagnetic