tick the correct answer

moving charges or electric currents produce ................fields.
1. magnetic
2. electric
3. both of them
4. none of these
The earth behaves as a magnet with the magnetic field pointing approximately from the geographic ..................
1. north to south
2. east to west
3. west to east
4. south to north
There is a ...................force when north poles ( or south poles ) of two magnets are brought close together
1. attractive
2. repulsive
3. both of them
4. none of these
a torroid of n turns , means radius R and crosssectional radius a carries I . it is placed on a horizontal tabel taken as x-y plane its magnetic moment m
1. is non zero and points in the z direction by symmetry
2. points along the axis of the torroid
3. is zero, otherwise there would be a field falling as 1/r3 at large distance outside r3 the torroid
4. is pointing radially outword
in a permanent magnet at room temperature
1. magnetic moment of each molecule is zero
2. the individual molecules have non zero magnetic moments which are all perfectly ligned
3. domains are partially aligned
4. domains are all perfectly aligned
A paramagnetic sample shows a net magnetisation of 8 Am-1 when placed in an external magnetic field of 0.6 T at a temperature of 4K. When the same sample is placed in an external magnetic field of 0.2 T at a temperature of 16 K, the magnetisation will be
1. 32/3 Am-1
2. 2/3 Am-1
3. 6Am-1
4. 2.4Am-1
Consider the two idealized systems:
(i) a parallel plate capacitor with large plates and small separation and
(ii) a long solenoid of length L » R, radius of cross-section. In
(i) E is ideally treated as a constant between plates and zero outside. In
(ii) magnetic field is constant inside the solenoid and zero outside. These idealised assumptions, however, contradict fundamental laws as below
1. case (i) contradicts Gauss’s law for electrostatic fields.
2. case (ii) contradicts Gauss’s law for magnetic fields.
3. case (i) agrees with ∫ E.dl = 0 .
4. case (ii) contradicts ∫ H.dl = Ien
S is the surface of a lump of magnetic material.
1. Lines of B are not necessarily continuous across S
2. Some lines of B must be discontinuous across S.
3. Lines of H are necessarily continuous across S.
4. Lines of H cannot all be continuous across S.
The primary origin(s) of magnetism lies in
1. Pauli exclusion principle.
2. polar nature of molecules.
3. intrinsic spin of electron.
4. none of these
A long solenoid has 1000 turns per metre and carries a current of 1 A. It has a soft iron core of μr = 1000. The core is heated beyond the Curie temperature, Tc .
1. The H field in the solenoid is (nearly) unchanged but the B field decreases drastically.
2. The H and B fields in the solenoid are nearly unchanged.
3. The magnetisation in the core reverses direction.
4. The magnetisation in the core does not diminishes.
Essential difference between electrostatic shielding by a conducting shell and magne-tostatic shielding is due to
1. electrostatic field lines cannot end on ’ charges and conductors do not have free charges.
2. lines of B can also end but conductors cannot end them.
3. lines of B cannot end. on any material and perfect shielding is not possible.
4. shells of high permeability materials cannot be used to divert lines of B from the interior region
Let the magnetic field on earth be modelled by that of a point magnetic dipole at the centre of earth. The angle of dip at a point on the geographical equator
1. is always zero
2. can be zero at specific points
3. cannot be positive or negative
4. is not bounded
A magnetic needle is kept in a non-uniform magnetic field. It experiences
1. a torque but not a force
2. neither a force nor a torque
3. a force and a torque
4. a force but not a torque
A 25 cm long solenoid has radius 2 cm and 500 total number of turns. It carries a current of 15 A. If it is equivalent to a magnet of the same size and magnetisation M¯¯¯¯¯¯, then |M¯¯¯¯¯¯| is
1. 3 π Am-1
2. 30000 π Am-1
3. 300 Am-1
4. 30000 Am-1
Three needles N1 N2 and N3 are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet, when brought close to them, will
1. attract N1 strongly, but repel N2 and N3 weakly
2. attract all three of them.
3. attract N1 and N2 strongly but repel N3.
4. attract N1 strongly, N2 weakly and repel N3 weakly.
Curie temperature is the temperature above which
1. a ferromagnetic material becomes paramagnetic
2. a ferromagnetic material becomes diamagentic
3. a paramagnetic material becomes diamagnetic.
4. a paramagnetic material becomes ferromagnetic.
The material suitable for making electromagnets should have
1. high retentivity and high coercivity.
2. low retentivity and low coercivity.
3. high retentivity and low coercivity.
4. low retentivity and high coercivity.
Curie law xT = constant, relating magnetic susceptibility (x) and absolute temperature (T) of magnetic substance is obeyed by
1. all magnetic substances.
2. paramagnetic substances.
3. diamagnetic substances
4. ferromagnetic substances.
Angle of dip is 90° at
1. poles
2. equator
3. both of them
4. tropic of cancer
Lines of force, due to earth’s horizontal magnetic field, are
1. elliptical
2. curved lines
3. concentric circles
4. parallel and straight
If the magnetising field on a ferromagnetic material is increased, its permeability.
1. is decreased
2. is increased
3. is unaffected
4. may be increased or decreased
The magnetic susceptibility of an ideal diamagnetic substance is
1. +1
2. 0
3. -1
4. ∞
the best material for teh ore of a transformer is
1. stainless steel
2. mild steel
3. hard steel
4. soft iron
Domain formation is the necessary feature of
1. diamagnetism
2. Paramagnetis
3. ferromagnetism
4. all of these
. In which type of material the magnetic susceptibility does not depend on temperature?
1. diamagnetic
2. paramagnetic
3. ferromagnetic
4. ferrite
A diamagnetic material in a magnetic field moves
1. perpendicular to the field.
2. from weaker to stronger parts.
3. from stronger to weaker parts.
4. in random direction.
The universal property among all substances is
1. diamagnetism
2. paramagnetism
3. ferromagnetism
4. all of these
Which of the following is correct about magnetic monopole?
1. Magnetic monopole exist
2. Magnetic monopole does not exist.
3. Magnetic monopole have constant value of monopole momentum.
4. The monopole momentum increase due to increase at its distance from the field
The earth behaves as a magnet with magnetic field pointing approximately from the geographic
1. North to South
2. South to North
3. East to West
4. West to East
Let the magnetic field on earth be modelled by that of a point magnetic dipole at the centre of earth. The angle of dip at a point on the geographical equator is
1. always zero
2. positive , negative or zero
3. unbounded
4. always negative

tick the correct answer

Quiz