CBSE Class 12 Physics Magnetism and Matter Worksheet Set A

CBSE Class 12 Physics Magnetism and Matter Worksheet Set A

Question. When a ferromagnetic material is heated to temperature above its Curie temperature, the material
(a) is permanently magnetized
(b) remains ferromagnetic
(c) behaves like a diamagnetic material
(d) behaves like a paramagnetic material

Answer: D

Question. A watch glass containing some powdered substance is placed between the pole pieces of a magnet. Deep concavity is observed at the centre. The substance in the watch glass is
(a) iron
(b) chromium
(c) carbon
(d) wood

Answer: A

Question. The work done in turning a magnet of magnetic moment M by an angle of 90° from the meridian, is n times the corresponding work done to turn it through an angle of 60°. The value of n is given by
(a) 2
(b) 1
(c) 0.5
(d) 0.25

Answer: A

Question. The B – H curve (i) and (ii) shown in fig. associated with 

(a) (i) diamagnetic and (ii) paramagnetic substance
(b) (i) paramagnetic and (ii) ferromagnetic substance
(c) (i) soft iron and (ii) steel respectively
(d) (i) steel and (ii) soft iron respectively

Answer: C

Question. A bar magnet is oscillating in the Earth’s magnetic field with a period T. What happens to its period and motion if its mass is quadrupled?
(a) Motion remains S.H. and period remains nearly constant
(b) Motion remains S.H. with time period = T/2
(c) Motion remains S.H. with time period = 2T
(d) Motion remains S.H. with time period = 4T

Answer: C

Question. Two magnets of magnetic moments M and 2M are placed in a vibration magnetometer, with the identical poles in the same direction. The time period of vibration is T₁. If the magnets are placed with opposite poles together and vibrate with time period T₂, then
(a) T₂ is infinite
(b) T₂ = T₁
(c) T₂ > T₁
(d) T₂ < T₁

Answer: C

Question. If θ₁ and θ₂ be the apparent angles of dip observed in two vertical planes at right angles to each other, then the true angle of dip q is given by :- 
(a) tan²θ = tan²θ1 + tan²θ₂
(b) cot²θ = cot²θ1 – cot²θ₂
(c) tan²θ = tan²θ1 – tan²θ₂
(d) cot²θ = cot²θ1 + cot²θ₂

Answer: D

Question. A compass needle placed at a distance r from a short magnet in Tan A position shows a deflection of 60º. If the distance is increased to r (3)1/3, then deflection of compass needle is
(a) 30º
(b) 60 x 3^1/3
(c) 60 x 3^2/3
(d) 60 x 3^3/3

Answer: A

Question. If horizontal and vertical components of earths magnetic field are equal, then angle of dip is
(a) 60°
(b) 45°
(c) 30°
(d) 90°

Answer: B

Question. The magnetic materials having negative magnetic susceptibility are
(a) non-magnetic
(b) para magnetic
(c) dia magnetic
(d) ferro magnetic

Answer: C

Question. For protecting a sensitive equipment from the external electric arc, it should be
(a) wrapped with insulation around it when passing current through it
(b) placed inside an iron can
(c) surrounded with fine copper sheet
(d) placed inside an aluminium can

Answer: B

Question. If a diamagnetic substance is brought near north or south pole of a bar magnet, it is
(a) attracted by the poles
(b) repelled by the poles
(c) repelled by north pole and attracted by the south pole
(d) attracted by the north pole and repelled by the south pole

Answer: B

Question. A bar magnet, of magnetic moment M̅ , is placed in a magnetic field of induction B̅ . The torque exerted on it is 
(a) M̅ . B̅
(b) -M̅ . B̅
(c) M̅ x B̅
(d) B̅ x M̅

Answer: C

Question. The main difference between electric lines of force and magnetic lines of force is
(a) electric lines of force are closed curves whereas magnetic lines of force are open curves
(b) electric lines of force are open curves whereas magnetic lines of force are closed curves
(c) magnetic lines of force cut each other whereas electric lines of force do not cut
(d) electric lines of force cut each other whereas magnetic lines of force do not cut

Answer: B

Question. Current i is flowing in a coil of area A and number of turns N, then magnetic moment of the coil M is
(a) NiA
(b) Ni/A
(c) Ni/√A
(d) N²Ai

Answer: A

Question. A diamagnetic material in a magnetic field moves
(a) perpendicular to the field
(b) from stronger to the weaker parts of the field
(c) from weaker to the stronger parts of the field
(d) None of these

Answer: B

Question. According to Curie’s law, the magnetic susceptibility of a substance at an absolute temperature T is proportional to
(a) T2
(b) 1/T
(c) T
(d) 1/T2

Answer: B

Question. The magnetic susceptibility is negative for : 
(a) diamagnetic material only
(b) paramagnetic material only
(c) ferromagnetic material only
(d) paramagnetic and ferromagnetic materials

Answer: A

Question. The magnetic moment of a diamagnetic atom is
(a) equal to zero
(b) much greater than one
(c) unity
(d) between zero and one

Answer: A

Question. There are four light-weight-rod samples A,B,C,D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted
(i) A is feebly repelled
(ii) B is feebly attracted
(iii) C is strongly attracted
(iv) D remains unaffected
Which one of the following is true ?
(a) B is of a paramagnetic material
(b) C is of a diamagnetic material
(c) D is of a ferromagnetic material
(d) A is of a non-magnetic material

Answer: A

Question. A thin bar magnet of length 2 l and breadth 2 b pole strength m and magnetic moment M is divided into four equal parts with length and breadth of each part being half of original magnet. Then the pole strength of each part is
(a) m
(b) m/2
(c) 2 m
(d) m/4

Answer: B

Question. A superconductor exhibits perfect :
(a) ferrimagnetism
(b) ferromagnetism
(c) paramagnetism
(d) diamagnetism

Answer: D

Question. A bar magnet 8 cms long is placed in the magnetic merdian with the N-pole pointing towards geographical north. Two netural points separated by a distance of 6 cms are obtained on the equatorial axis of the magnet. If horizontal component of earth’s field = 3.2 × 10^–5 T, then pole strength of magnet is
(a) 5 ab-amp × c
(b) 10 ab-amp × cm
(c) 2.5 ab-amp × cm
(d) 20 ab-amp × cm

Answer: A

Question. A steel wire of length l has a magnetic moment M. It is bent in L-shape (Figure). The new magnetic moment is

(a) M
(b) M/√2
(c) M/2
(d) 2M 

Answer: B

Question. The force between two short bar magnets with magnetic moments M₁ and M₂ whose centres are r metres apart is 8 N when their axes are in same line. if the separation is increased to 2 r, the force between them in reduced to
(a) 4 N
(b) 2 N
(c) 1 N
(d) 0.5 N

Answer: D

Question. Horizontal component of earth's field at a height of 1 m from the surface of earth is H. Its value at a height of 10 m from surface of earth is
(a) H/10
(b) H/9
(c) H/100
(d) H

Answer: D

Question. Two isolated point poles of strength 30 A-m and 60 A-m are placed at a distance of 0.3m. The force of repulsion is
(a) 2 × 10^–3 N
(b) 2 × 10^–4 N
(c) 2 × 10⁵ N
(d) 2 × 10^–5 N

Answer: A

Question. The magnetic moment of a magnet is 0.1 amp × m². It is suspended in a magnetic field of intensity 3 × 10^–4 weber/m².
The couple acting upon it when deflected by 30º from the magnetic field is
(a) 1 × 10^–5 N m
(b) 1.5 × 10^–5 N m
(c) 2 × 10^–5 N m
(d) 2.5 × 10^–5 N m

Answer: B

Question. When 2 ampere current is passed through a tangent galvanometer, it gives a deflection of 30º. For 60º deflection, the current must be
(a) 1 amp.
(b) 2 3 amp.
(c) 4 amp.
(d) 6 amp.

Answer: D

Question. Two identical bar magnets are fixed with their centres at a distance d apart. A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figure. The force on the charge Q is
(a) directed perpendicular to the plane of paper
(b) zero
(c) directed along OP
(d) directed along PO

Answer: B

Question. Two tangent galvanometers having coils of the same radius are connected in series. A current flowing in them produces deflections of 60º and 45º respectively. The ratio of the number of turns in the coils is
(a) 4/3
(b) √3 + 1/1
(c) √3 + 1/√3 - 1
(d) √3/1

Answer: D

Question. The moment of a magnet (15 cm × 2 cm × 1 cm) is 1.2 A-m².
What is its intensity of magnetisation?
(a) 4 × 10⁴ A m^–1
(b) 2 × 10⁴ A m^–1
(c) 10⁴ A m^–1
(d) None of these

Answer: A

Question. In the above question, magnetic moment of each part is
(a) M/4
(b) M
(c) M/2
(d) 2 M

Answer: A

Question. In end on and broadside on position of a deflection magnetometer, if θ1 and θ2 are the deflections produced by short magnets at equal distances, then tan θ₁/ tan θ₂ is
(a) 2 : 1
(b) 1 : 2
(c) 1 : 1
(d) None of these

Answer: A

Question. If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by md, mp and mf respectively, then
(a) μ_d = 0 and μ_p ≠ 0
(b) μ_d ≠ 0 and μ_p = 0
(c) μ_p = 0 and μ_f ≠ 0
(d) μ_d ≠ 0 and μ_f ≠ 0

Answer: A

Question. Two bar magnets of the same mass, same length and breadth but having magnetic moments M and 2M are joined together pole for pole and suspended by a string. The time period of assembly in a magnetic field of strength H is 3 seconds. If now the polarity of one of the magnets is reversed and combination is again made to oscillate in the same field, the time of oscillation is
(a) √3 sec
(b) 3 √3 sec
(c) 3 sec
(d) 6 sec

Answer: B

Question. Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show
(a) anti ferromagnetism
(b) no magnetic property
(c) diamagnetism
(d) paramagnetism

Answer: D

Question. Two magnets are held together in a vibration magnetometer and are allowed to oscillate in the earth’s magnetic field with like poles together. 12 oscillations per minute are made but for unlike poles together only 4 oscillations per minute are executed. The ratio of their magnetic moments is
(a) 3 : 1
(b) 1 : 3
(c) 3 : 5
(d) 5 : 4

Answer: D

Question. A curve between magnetic moment and temperature of magnet is 

Answer: C

Question. The line on the earth surface joining the point where the field is horizontal, is called
(a) magnetic equator
(b) magnetic line
(c) magnetic axis
(d) magnetic inertia

Answer: A

Question. A vibration magnetometer placed in magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of 2 sec in earth's horizontal magnetic field of 24 microtesla. When a horizontal field of 18 microtesla is produced opposite to the earth's field by placing a current carrying wire, the new time period of magnet will be
(a) 1 s
(b) 2 s
(c) 3 s
(d) 4 s

Answer: D

Question. Consider the two idealised 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
(a) case (i) contradicts Gauss’ law for electrostatic fields
(b) case (ii) contradicts Gauss’ law for magnetic fields
(c) case (i) agrees with ∮ E.dl = 0.
(d) case (ii) contradicts ∮ H.dl = Ien

Answer: B
 

              Very Short Answer

Q1)       Define dynamo effect?

Q2)       What is coercivity?

Q3)       Where we can use electromagnets?

Q4)       What is Gauss, law for magnetism?

Q5)       Why core of electromagnets are made up of Ferro magnets material?

             

              Short Answer

Q6)       What is magnetic intensity?

Q7)       What happens to compass needle at Earth's pole?

Q8)       What do you mean by the term earth’s magnetism?

Q9)       Why solenoid acts as a bar magnet?

Q10)     What do you understand by the magnetic declination and dip?

             

              Long Answer

Q11)     State the difference between bar magnet and electromagnets?

Q12)     What are the common ideas regarding the magnetisms?

Q13)     Write short note on ferromagnetism?

Q14)     Explain magnetic fields lines and its properties?

Q15)     State the difference between paramagnetism and diamagnetism?