CBSE Questions for Class 12 Medical Physics Magnetism And Matter Quiz 2 - MCQExams.com

$$\chi _{1}$$and $$\chi _{2}$$  are susceptibilities of a diamagnetic substance at temperatures $$T_{1}K$$ and $$T_{2}K$$  respectively, then,
  • $$\chi _{1}T_{1}=\chi _{2}T_{2}$$
  • $$\chi _{1}=\chi _{2}$$
  • $$\chi _{1}\sqrt{T_{1}}=\chi _{2}\sqrt{T_{2}}$$
  • $$\chi _{1}T_{2}=\chi _{2}T_{1}$$
Curie's law states that magnetic susceptibility is
  • inversely proportional to the absolute temperature
  • exponentially related to temperature
  • directly proportional to the absolute temperature
  • does not depend on temperature
The core of electromagnet is made of soft iron, because
a) susceptibility of soft iron is very high
b) coercivity of soft iron is very low
  • only a is correct
  • only b is correct
  • both a and b are correct
  • both a and b are wrong

Susceptibility is small and negative for
  • para magnetic
  • diamagnetic
  • ferro magnetic
  • electromagnetic

At Curie temperature, in ferromagnetic materials
  • the atomic dipoles get aligned
  • the atomic dipoles remains stationary
  • the atomic dipoles lose alignment
  • magnetism is zero

A magnetic pole of pole strength 9.2 A m. is placed in a field of induction 50x10$$^{-6}$$ Tesla. The force experienced by the pole is :
  • 46N
  • 46$$\times$$10$$^{-4}$$N
  • 4.6$$\times$$10$$^{-4}$$N
  • 460N

The magnetic induction at a distance d from the magnetic pole of the unknown strength m is B. If an identical pole is now placed at a distance of 2d from the first pole, the force between the two poles is          
  • mB
  • $$\frac{mB}{2}$$
  • $$\frac{mB}{4}$$
  • 2mB

Two short magnets each of moment $$10 A-m^{2}$$ are placed in end - on position so that their centres are $$0.1\ m$$ apart. The force between them is
  • $$0.4N$$
  • $$0.5N$$
  • $$0.6N$$
  • $$0.8N$$

To explain ferromagnetism, we use
  • orbital electron hypothesis
  • spinning electron hypothesis
  • domain theory
  • Langevin theory

In the hystersis cycle, the value of H needed to make the intensity of magnetisation zero is called
  • retentivity
  • coercivity
  • Lorentz force
  • Pseudo force

Force between two identical bar magnets whose centres are  $$r$$ meters apart is $$4.8 N,$$ when their axis are in the same line. If the separation is increased to $$2r$$ meters, the force between them is reduced to:
  • 2.4 N
  • 1.2 N
  • 0.6 N
  • 0.3 N

The value of susceptibility for super conductor is
  • 0
  • $$\infty $$
  • +1
  • -1

If the magnetic moment of magnet is $$0.8 \times 10^{-3}\ Am^{2}$$ and the force acting on each pole in a uniform magnetic field strength of $$0.48\ gauss$$, is $$0.512 \times 10^{-6}N$$ . The distance between the poles of the magnet is : (in $$cm $$)
  • $$25$$
  • $$12.5$$
  • $$15$$
  • $$7.5$$

The force acting on a pole of strength of 20 Am is 8x10$$^{-4}$$ N, when placed in a magnetic field. The magnetic induction field strength is :
  • 4$$\times $$10$$^{-6}$$ T
  • 0.4$$\times $$10$$^{4}$$ T
  • 4 G
  • 4$$\times $$10$$^{-5}$$ T

Two equal poles repel each other with a force of 10$$^{-3}$$ N. When placed 2cm apart in air, the pole strength of each is (in amp-m).
  • 4$$\pi $$
  • 2
  • 4
  • 2$$\pi $$
The purpose of soft iron cylinder between the pole pieces of the horse-shoe magnet in a moving coil galvanometer is 
  • to increase the magnetic induction in the polar

    gap
  • to evenly distribute the magnetic lines of force
  • to provide a radial magnetic field
  • to reduce the magnetic flux leakage in the polar

    gap
Complete the following statements with an appropriate word / term to be filled in the blank space(s). 
The magnetic lines of force are the lines drawn in a magnetic field along which a _______ pole would move.
  • south magnetic
  • north magnetic
  • north and south magnetic
  • north-east
How do bars of bismuth set their length when are placed between the magnetic poles?
  • Perpendicular to the lines of force
  • Along the lines of force
  • Neither perpendicular nor along the lines of force
  • In any direction
According to Curie's law, the magnetic susceptibility of a substance at an absolute temperature T is proportional to -
  • $$1/T$$
  • $$T$$
  • $$1/T$$$$^{2}$$
  • $$T$$$$^{2}$$
The SI unit of magnetic field is:
  • Tesla
  • Weber
  • Weber.m
  • Gauss
Complete the following statements with an appropriate word / term to be filled in the blank space(s). 
Field lines are used to represent a:
  • magnetic field
  • magnetic force
  • magnetic current
  • magnetic dipole
Complete the following statements with an appropriate word / term to be filled in the blank space(s).
Field lines are shown closer together where the magnetic field is:
  • less
  • constant
  • greater
  • none of these
The force with which a magnet attracts objects like iron is called ....................... .
  • Electric Force
  • Magnetic Force
  • Electromagnetic faoce
  • gravitational force
A small piece of a substance  is repelled when it is brought near a powerful magnet. What can you say about its type ?
  • dimagnetic
  • paramagnetic
  • ferromagnetic
  • non-magnetic
How will  the force between the two poles change if the two poles are connected by an iron rod keeping the distance between two magnetic poles constant ?
  • Increases
  • Decreases
  • Remains same
  • None of these
State whether true or false.
Magnetic lines of force are primarily curved lines.
  • True
  • False
Which of the following figures depict non uniform magnetic field?
What is the unit of magnetic flux?
  • Dynes
  • Oerested
  • Gauss
  • Weber
Lines of force
  • are not imaginary lines
  • cannot be mapped on paper
  • do not intersect each other
  • always intersect each other
 Magnetic field lines :
  • starts from north pole
  • starts from south pole
  • starts from current-carrying wires
  • are closed loops
The magnetising field required to be applied in opposite direction to reduce residual magnetism to zero is called
  • coercivity
  • retentivity
  • hysteresis
  • none of these
A bar magnet has coercivity $$4\times10^3 Am^{-1}$$. It is placed in a solenoid having $$40$$ turns per cm and is $$1.2m$$ long. The current carried by the solenoid to demagnetize  the bar magnet is :
  • $$6A$$
  • $$8A$$
  • $$5.78A$$
  • none of these
A magnetic field can be produced by :
  • A moving charge
  • A changing electric field
  • None of these
  • Both of these
At Curie temperature the ferromagnetic materials get converted into.
  • non-magnetic material.
  • para magnetic material.
  • dia magnetic material.
  • all of the above.
Figure shows a some of the equipotential surface of the magnetic scalar potential. The magnetic field at a point in the region is :

146279.JPG
  • $$2\times10^{-5}T$$
  • $$10^{-5}T$$
  • $$10^{-4}T$$
  • $$2\times10^{-4}T$$
A powerful magnet attracts
  • all materials.
  • only ferromagnetic materials and their ores.
  • some materials and repels some other materials.
  • only iron and its ores but does not repel any material.
Which of the following are best suited to make the core of a transformer?
  • soft iron
  • steel
  • alnico
  • none of these
The value of Curie temperature for $$Ni$$ is nearly 
  • $$631K$$
  • $$770K$$
  • $$890K$$
  • $$1100K$$
Two magnetic lines of force:
  • never cut each other
  • cut near the poles
  • cut according to the position of the magnet
  • cut at neutral points
A current carrying wire in the neighbourhood produces -
  • No field
  • Electric field only
  • Magnetic field only
  • Electric and magnetic fields
Which of the following cannot be ferromagnetic?
  • alloys
  • solids
  • liquids
  • gases
If a diamagetic solution is poured into a U-tube and one arm of this U-tube is placed between the poles of a strong magnet, with the meniscus in line with the field, then the level of solution will :
  • rise
  • fall
  • oscillate slowly
  • remain as such
What is the direction of magnetic field at the centre of a coil carrying  clockwise current ?
  • No direction
  • normal to the axis of coil inwards.
  • Along the axis of coil inwards.
  • Along the axis of coil outwards.
The space around a magnet where its influence can be detected is called ..............
  • curve
  • magnetic field
  • magnetic needle
  • horse shoe
The magnetic lines of force around a very weak magnet are :
  • overlapping each other
  • parallel lines
  • not close continuous curves
  • close continuous curves
Which of the following is/are true for "magnetic lines of force around a bar magnet"?
  • are closed continuous curves
  • travel from north to south outside the magnet
  • bend around the length of magnet
  • all the above
A straight wire lying in a horizontal plane carries a current from north to south.  What will be the direction of magnetic field at a point just underneath it?
  • Towards north.
  • Towards east.
  • Towards west.
  • Towards south.
Magnetic lines of force can pass through:
  • only magnetic substances
  • only non-magnetic substances
  • both (a) and (b)
  • none of the above
Magnetic lines do not intersect one-another because:
  • they are at a distance
  • they are in the same direction
  • they are parallel to one another
  • in the point of intersection there will be two direction of the magnetic field, which is impossible
The strength of magnetic field around a bar magnet :
  • decrease with the decrease in distance from the magnet
  • decrease with the increase in distance from the magnet     
  •  remain constant with increase in distance from magnet
  • becomes zero with decrease  in distance from magnet
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