CBSE Questions for Class 12 Medical Physics Magnetism And Matter Quiz 6 - MCQExams.com

Two magnetic poles one of which is three times as strong as the other exert on each other, a force equal to $$3×10^{−3}$$ when separated by a distance of $$10\ cm$$. The strength of the each pole is
  • $$5\ Am, 15\ Am$$
  • $$30\ Am, 10\ Am$$
  • $$20\ Am, 60\ Am$$
  • $$50\ Am, 150\ Am$$

When a diamagnetic liquid is poured into a U-tube and one arm of the U-tube is placed between the two poles of strong magnet with the meniscus along the lines of the field, then the level of the liquid in the arm where magnetic field is applied will
  • fall
  • rise
  • oscillate
  • remain unchanged

A sensitive magnetic instrument can be shielded very effectively from outside magnetic fields by placing it inside a box of:
  • wood
  • plastic
  • metal of high conductivity
  • soft iron of high permeability
Two equal poles each repel with a force of 10 newtons when placed 2 cm apart in air. The pole-strength of each in amp-meter is
  • $$10^{3}$$
  • $$\dfrac {10^{3}}{2\pi }$$
  • $$2\pi \times 10^{3}$$
  • $$2\times 10^{2}$$

Two magnetic poles have their strengths in the ratio 3 :They are kept at a distance of 0.6 m in air and the force of repulsion is found to be 0.06 dynes. The pole strengths are (in amp. m)
  • 1.8, 1.2
  • 18, 12
  • 6, 4
  • 0.6, 3.6

The pole strength of a bar magnet is 2 Am. If the field at poles are 0.2 T and 0.22 T, then the force acting on the bar magnet is

( consider field direction to be same)
  • 0.4N
  • 0.04N
  • 0.44N
  • 0.8N
When two magnetic poles one of which is four times greater than the other in pole strength, are placed 5 cm apart in air. They exert a mutual force of 144 mg.wt. on each other. The pole strengths of the poles are (in ampere metre)
(g=10 m/s$$^{2}$$)
  • 6, 3
  • 9, 3
  • 12, 3
  • 18, 6
Choose the incorrect statement from the following regarding magnetic lines of force.
  • The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points
  • Magnetic field lines are closed curves
  • If magnetic field lines are parallel and equidistant, they represent zero field strength
  • Relative strength of magnetic field is shown by the degree of closeness of the field lines
Which of the following cannot be deflected by a

magnetic field?
  • Alpha rays
  • Beta rays
  • Gamma rays
  • Cosmic rays
The material for making permanent magnets should have 
  • high retentivity, high coercivity
  • high retentivity, low coercivity
  • low retentivity, high coercivity
  • low retentivity, low coercivity

A bar Magnet of Magnetic Moment 3.0 amp.m$$^{2}$$ is placed in a uniform Magnetic induction field 2 x 10$$^{-5}$$ T. If each pole of the magnet experience a force of 6 x 10$$^{-4}$$ N, the length of the magnet is
  • 05 m
  • 0.3 m
  • 0.2 m
  • 0.1 m
The force between two magnetic poles reduces to $$aN$$, if distance between them is increased to $$n$$ times and it increases to $$bN$$ if the distance between them is $$1/n^{th}$$ the original value. Then $$a:b$$ is :
  • $$1:n^{2}$$
  • $$n^{2}$$:1
  • $$n^{4}$$:1
  • $$1:n^{4}$$

Two magnetic poles of strengths 10 Am and 20 Am are separated by a distance of 10 cm. The ratio of force on them is
  • 1 : 1
  • 1: 2
  • 2 : 1
  • 1 : 4
Force acting between two small magnets, placed in end on position $$0.1m$$ apart from their centres is 
(Given magnetic moment of each magnet is $$5Am^{2}$$ )
  • $$0.6N$$
  • $$0.8N$$
  • $$0.15N$$
  • $$0.2N$$

Two poles of same strength attract each other with a force of magnitude $$F$$ when placed at the corners of an equilateral triangle. If a north pole of the same strength is placed at the third vertex, it experiences a force of magnitude
  • $$F\sqrt{3}$$
  • $$F$$
  • $$F\sqrt{2}$$
  • $$2F$$

Relative permittivity and permeability of a material are $$\varepsilon _{r}$$ and $$\mu _{r}$$ respectively. The values of these quantities allowed for a diamagnetic material are
  • $$\varepsilon _{r}=0.5,\mu _{r}=1.5$$
  • $$\varepsilon _{r}=1.5,\mu _{r}=0.5$$
  • $$\varepsilon _{r}=0.5,\mu _{r}=0.5$$
  • $$\varepsilon _{r}=1.5,\mu _{r}=1.5$$
A pole of pole strength $$80 Am$$ is placed at a point at a distance $$20cm$$ on the equatorial line from the centre of a short magnet of magnetic moment $$20Am^2$$. The force experienced by it is
  • $$8\times 10^{-2}N$$
  • $$2\times 10^{-2}N$$
  • $$16\times 10^{-2}N$$
  • $$64\times 10^{-2}N$$
Assertion: The earths magnetic field is due to iron present in its core
Reason: At a high temperature magnet loses its magnetic property or magnetism
  • Both A and R are true and R is the correct explanation of A
  • Both A and R are true and R is not correct explanation of A
  • A is true, but R is false
  • A is false, but R is true
Assertion: The properties of paramagnetic and ferromagnetic substances are not affected by heating.
Reason: As temperature rises, the alignment of molecular magnets gradually decreases.
  • Both A and R are true and R is the correct explanation of A
  • Both A and R are true and R is not correct explanation of A
  • A is true, but R is false
  • A is false, but R is true
Choose the correct statement.
  • The magnetic field due to current carrying conductor lie in a plane parallel to the conductor.
  • The magnetic field due to current carrying conductor is uniform in a plane perpendicular to the conductor.
  • The magnetic field due to current carrying conductor is non uniform in a plane perpendicular to the conductor.
  • The magnetic field due to current carrying conductor is zero in a plane perpendicular to the conductor.

Substances in which the magnetic moment of a

single atom is not-zero
  • diamagnetic
  • ferromagnetic
  • paramagnetic
  • electromagnetic
At a place the value of $$B_{H}$$ and $$B_{V}$$ are  $$0.4\times 10^{-4}$$and $$0.3\times 10^{-4}$$respectively. The resultant earths magnetic field is :
  • $$0.5\times 10^{-4}T$$
  • $$10^{-4}T$$
  • $$2\times 10^{-4}T$$
  • $$5\times 10^{-4}T$$
Assertion: A soft iron core is used in a moving coil galvanometer to increase the strength of magnetic field
Reason: From soft iron more number of the magnetic lines of force passes
  • Both A and R are true and R is the correct explanation of A
  • Both A and R are true and R is not correct explanation of A
  • A is true, but R is false
  • A is false, but R is true
A bar of soft iron is placed flat on the table. A bar magnet is taken and its south pole is placed on one end of the bar of soft iron. The magnet is held almost vertically. The bar is stroked from one end to the other with magnet. On the other end of the bar, magnet is lifted and again placed on the first end and the bar is again stroked. At which  end of the bar where the magnet is lifted ?
  • South pole
  • No pole
  • South and north both type
  • North pole
When a charged particle moves through a magnetic

field, it undergoes a change in its 
  • energy.
  • mass.
  • speed.
  • direction of motion.
Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature then it will show 
  • diamagnetism
  • paramagnetism
  • anti ferromagnetism
  • no magnetic property
........................ Line joining any two points in the direction of magnetic field.
  • Magnetic Lines of Force
  • Magnetic inductions
  • Both (a) and (b)
  • None of these
Three specimens of magnetic material were tested using the apparatus shown in the diagram.

When the switch is closed, the specimen picks up some of the iron nails but when the switch is opened, many or most of the nails fall off. The number of nails picked up and left on were found for three specimens. The table shows the results.
SpecimenNumber of nails picked up Number of nails left on
X    35    4
Y    20    10
Z    40    3

Which among the following pair of elements are suitable in the construction of electric bell?
93932_a548f45a7101479c862ccb8800d29593.png
  • X, Y
  • Y, Z
  • X, Z
  • X, Y, Z
Which of the following figures represents the magnetic lines of force due to an isolated north pole? 
Magnetic field due to a short bar magnet on its equatorial line at a certain distance is $$B$$. Find out its value at the same distance on the axial line? 
  • $$2B$$
  • $$\displaystyle \dfrac{B}{2}$$
  • $$3B$$
  • $$\displaystyle \dfrac{B}{3}$$
If cathode rays enter a magnetic field making an oblique angle with lines of induction, then their path in the magnetic field is
  • A straight line
  • Helix
  • A circle
  • Parabole
A bar magnet is placed in the north-south direction with its north pole towards north. In which direction from the centre of the magnet will the points of zero magnetic filed lie?
  • North-South
  • East-West
  • North-East-West
  • None of these
Space around a magnet in which the magnetic pole experiences a force is called
  • Electric field
  • Magnetic field
  • Induced field
  • None of these
State whether true or false :
Outside the magnet, the magnetic lines of forces pass from north pole to the south pole and inside the magnet, they pass from south to the north pole. 
  • True
  • False
Which of the following is/are correct about magnetic lines of force ?
  • Are mere directions
  • Have no physical reality
  • Can be used to indicate the direction of the magnetic field at a point
  • All of these
If the distance between two unlike poles is doubled then the force of attraction between them becomes ........................... times its original value.
  • $$\dfrac{1}{2}$$
  • $$\dfrac{1}{4}$$
  • 2
  • 4
How will you quantize the relative permeability of a paramagnetic substance ?
  • Much more than one
  • Slightly more than one
  • Less than one but greater than zero
  • Zero
Ferromagnetic substances achieve a high degree of magnetic alignment due to the effect known as 
  • Pole swapping
  • Exchange coupling
  • Magnetic poling
  • None of these
The distance between two magnetic poles is doubled and their pole-strength is also doubled. The force between them :
  • Increases to three times
  • Decreases by half
  • Remains unchanged
  • Increases to two times
A unit magnetic pole is that pole which repels an identical pole at a 1 meter distance with a force of ________.
  • $$10^{-6}N$$
  • $$10^{-7}N$$
  • $$10^{-5}N$$
  • $$10^{-4}N$$
Magnetic lines of force can never intersect.
  • True
  • False
The magnetic lines of force due to a bar magnet are :
  • Curved lines
  • Curved closed loops
  • Concentric circles
  • Parallel and straight
Two magnetic monopoles are kept apart by a distance 'd'. The magnetic force acting on each pole is 'F'. How much percentage must the distance between the magnetic poles be changed so that the magnetic force acting on each pole be 4F.
  • -10%
  • -20%
  • -40%
  • -50%
The space around the magnet in which another magnetic pole placed experiences a magnetic force is the region of magnetic field.
  • True
  • False
Magnetic lines of force: 
  • Always intersect.
  • Are closed curves.
  • Intersect far away from the poles
  • Do not pass through vacuum.
The corecivity of a small magnet where the ferromagnet gets demagnetized is $$3 \times 10^3 Am^{-1}$$. The current required to be passed in a solenoid of length $$10 cm$$ and number of turns $$100$$, so that the magnet gets demagnetized when inside the solenoid is:
  • $$3A$$
  • $$6A$$
  • $$30 mA$$
  • $$60 mA$$
Two magnetic poles each of magnetic pole strength 16 A m are placed at a distance of 2 m apart. Find magnetic force acting on each pole.
  • $$4 \times 10^{-7}N$$
  • $$16 \times 10^{-7}N$$
  • $$32 \times 10^{-7}N$$
  • $$64 \times 10^{-7}N$$
The north poles of pole strengths m, 9m are kept apart by a certain distance. Find the distance of full point from larger pole.
  • $$\dfrac{3d}{4}$$
  • $$\dfrac{3d}{8}$$
  • $$\dfrac{3d}{16}$$
  • $$\dfrac{3d}{2}$$
State whether true or false.
Magnetic lines of force are imaginary lines.
  • True
  • False
State whether true or false.
Magnetic lines of force emanate from the south pole and enter into the north pole.
  • True
  • False
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