CBSE Class 12 Physics Magnetism Worksheet Set A

Magnetism MCQ Questions with Answers Class 12 Physics

Question. Which one of the following statement is not correct about the magnetic field ?    
(a) Inside the magnet the lines go from north pole to south pole of the magnet
(b) Tangents to the magnetic lines give the direction of the magnetic field
(c) The magnetic lines form a closed loop
(d) Magnetic lines of force do not cut each other

Answer    A

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 simple harmonic with time period = T/2
(b) Motion remains S.H.M with time period = 2T
(c) Motion remains S.H.M with time period = 4T
(d) Motion remains S.H.M and period remains nearly constant 

Answer    B

Question. Liquid oxygen remains suspended between two pole forces of a magnet because it is :   
(a) diamagnetic
(b) paramagnetic
(c) ferromagnetic
(d) antiferromagnetic

Answer    B

Question. Two bar magnets having same geometry with magnetic moments M and 2M, are firstly placed in such a way that their similar poles are in same side then its time period of oscillation is T₁. Now the polarity of one of the magnet is reversed then time period of oscillation is T2, then    
(a) T1 < T2
(b) T1 = T2
(c) T1 > T2
(d) T2 = ∞ 

Answer    A

Question. A frog can be levitated in a magnetic field produced by a current in a vertical solenoid placed below the frog. This is possible because the body of the frog behaves as :   
(a) paramagnetic
(b) diamagnetic
(c) ferromagnetic
(d) antiferromagnetic

Answer    C

Question. A bar magnet of magnetic moment M is cut into two parts of equal length. The magnetic moment of each part will be   
(a) M
(b) 2M
(c) zero
(d) 0.5M 

Answer    D

Question. The best material for the core of a transformer is   
(a) mild steel
(b) stainless steel
(c) soft iron
(d) hard steel 

Answer    C

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) 1/2
(b) 1/4
(c) 2
(d) 1 

Answer    C

Question. Which one of the following are used to express intensity of magnetic field in vacuum ?   
(a) oersted
(b) tesla
(c) gauss
(d) none of these

Answer    A

Question. At a point A on the earth’s surface the angle of dip, d = +25°. At a point B on the earth’s surface the angle of dip, d = –25°. We can interpret that (a) A and B are both located in the southern hemisphere.     
(b) A and B are both located in the northern hemisphere.
(c) A is located in the southern hemisphere and B is located in the northern hemisphere.
(d) A is located in the northern hemisphere and B is located in the southern hemisphere.

Answer    D

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

Answer    A

Question. A magnet 10 cm long and having a pole strength 2 amp m is deflected through 30° from the magnetic meridian. The horizontal component of earth’s induction is 0.32´10-4 tesla then the value of deflecting couple is:   
(a) 32 ´10-7Nm
(b) 16 ´10-7Nm
(c) 64 ´10-7Nm
(d) 48 ´10-7Nm
 

Answer    A

Question. A bar magnet of magnetic moment M is placed at right angles to a magnetic induction B. If a force F is experienced by each pole of the magnet, the length of the magnet will be   
(a) MB/F
(b) BF/M
(c) MF/B
(d) F/MB

Answer    C

Question. Angle of dip is 90° at:    
(a) Equator
(b) Middle point
(c) Poles
(d) None of these

Answer    C

Question. A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It    
(a) will become rigid showing no movement
(b) will stay in any position
(c) will stay in north-south direction only
(d) will stay in east-west direction only 

Answer    B

Question. Tangent galvanometer is used to measure   
(a) potential difference
(b) current
(c) resistance
(d) charge.

Answer    B

Question. Curie temperature is the temperature above which   
(a) a ferromagnetic material becomes paramagnetic
(b) a paramagnetic material becomes diamagnetic
(c) a ferromagnetic material becomes diamagnetic
(d) a paramagnetic material becomes ferromagnetic

Answer    A

Question. An iron rod of susceptibility 599 is subjected to a magnetising field of 1200 A m–1. The permeability of the material of the rod is (m0 = 4p × 10^–7 T m A^–1)     
(a) 2.4p × 10^–4 T m A^–1
(b) 8.0 × 10^–5 T m A^–1
(c) 2.4p × 10^–5 T m A^–1
(d) 2.4p × 10^–7 T m A^–1

Answer    A

Question. A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy.      
The work required to do this comes from
(a) the current source
(b) the magnetic field
(c) the lattice structure of the material of the rod
(d) the induced electric field due to the changing magnetic field 

Answer    A

Question. The north pole of a magnet is brought near a metallic ring. Then the direction of the induced current in the ring will be:   
(a) Towards north
(b) Towards south
(c) Anticlockwise
(d) Clockwise

Answer    C

Question. Electromagnets are made of soft iron because soft iron has      
(a) low retentivity and high coercive force
(b) high retentivity and high coercive force
(c) low retentivity and low coercive force
(d) high retentivity and low coercive force

Answer    C

Question. At a temperatur of 30°C, the susceptibility of a ferromagnetic material is found to be c . Its susceptibility at 333°C is    
(a) c
(b) 0.5 c
(c) 2c
(d) 11.1c

Answer    B

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

Answer    C

Question. A magnet makes 40 oscillation per minute at a place having magnetic intensity of 0.1 × 10^–5 tesla. At another place it takes 2.5 sec to complete one oscillation. The value of earth's horizontal field at that place is    
(a) 0.76 × 10^–6 tesla
(b) 0.18 × 10^–6 tesla
(c) 0.09 × 10^–6 tesla
(d) 0.36 × 10^–6 tesla

Answer    D

Question. The materials suitable for making electromagnets should have   
(a) high retentivity and low coercivity
(b) low retentivity and low coercivity
(c) high retentivity and high coercivity
(d) low retentivity and high coercivity

Answer    B

MAGNETISM

Test Paper-I

1 What is gyromagnetic ratio? Give the value of it.

2 What is Bohr magneton? Find the value of it.

3 Show that an electron moving around the central nucleus has a magnetic moment μl is given by μl = 𝑒𝑙/2𝑚 where l is the magnitude of the angular momentum of the circulating electron about the central nucleus.

4 Fill-in the blanks. .

a. The earth behaves as a magnet with the magnetic field pointing from _______to ______.

b. When a bar magnet is freely suspended, it points in the __________ direction. The tip which points to the geographic north is called the _________ pole and the tip which points to the geographic south is called the __________ of the magnet.

c. Magnetic ______poles do not exist.

5 Give the properties of magnetic field lines. 

6 Give the points basing on which we can consider a bar magnet as equivalent to a solenoid. 

7 Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. Why?

8 If magnetic monopoles existed, how would the Gauss’s law of magnetism be modified?

9 Magnetic field arises due to charges in motion. Can a system have magnetic moments even though its net charge is zero? Page:184

10 What is dynamo effect?

11 What is the angle made by the axis of earth’s magnetic dipole with that of axis of rotation of the earth? Give the locations of earth’s magnetic north pole and that of the earth’s magnetic south pole. ?

12 The earth’s magnetic field at the equator is approximately 0.4 G. Estimate the earth’s dipole moment. ?

13 What are the elements of earth’s magnetic field?

14 Define magnetic declination. What is its value in India? What is the significance of this value?

15 What is angle of dip? How a magnetic needle gets tilted in the northern and southern hemisphere of the earth?

16 In the magnetic meridian of a certain place, the horizontal component of the earth’s magnetic field is 0.26G and the dip angle is 60⁰. What is the magnetic file of the earth at this location?

17 Explain briefly what happens to the magnetic needle at the poles?

18 State Gauss’s law in magnetism.

MAGNETISM

Test Paper-II

1 What are diamagnetic substances? Briefly explain what is the cause for diamagnetism?
Give any two examples of diamagnetic substances.

2 What type of materials are superconductors? Give any one application of a superconductor. 

3 What are paramagnetic materials? Give an example. How do they behave inside an external magnetic field?

4 What is Curie’s law? State the factors on which the susceptibility and relative permeability of a paramagnetic material depends upon. What is the effect of increasing the field on a paramagnetic material?

5 What is a Ferro magnetic substance? What is the importance of a domain in a ferromagnetic substance?

6 What are hard and soft Ferro magnets? Give examples for the same. Name the material that is used in permanent magnets. 

7 What is the effect of temperature on a Ferromagnetic substance? How is related to curie temperature? How susceptibility is related to temperature for a temperature above the curie temperature.

8 What are permanent magnets? Give different ways of making a permanent magnet. Also state what is the efficient way to make a permanent magnet? 

9 What are the properties of a material so that it can be used in making permanent magnet? Give any two examples for the same.

10 Give the properties of a material that can be used as a Core of electromagnets .Give an example for the same.

11 Briefly explain how a soft iron core in solenoid acts as an electromagnet?

12 Give the properties of a material that can be used in transformer cores.

13 Give any two applications of electromagnets.

14 A magnetic needle in a uniform magnetic field experiences a torque but not net force. An iron nail near a bar magnet, however, experiences a force of attraction in addition to a torque. Why?