Monday, January 3, 2022

H C Verma solutions, MAGNETIC PROPERTIES OF MATTER, Chapter-37, OBJECTIVE-I, Concepts of Physics, Part-II

Magnetic Properties of Matter


OBJECTIVE-I


    1.  A paramagnetic material is placed in a magnetic field. Consider the following statements:  

(A) If the magnetic field is increased, the magnetization is increased.

(B) If the temperature is increased the magnetization is increased. 

  (a) Both A and B are true.

  (b) A is true but B is false. 

  (c) B is true but A is false. 

  (d) Both A and B are false.        


ANSWER: (b)   


EXPLANATION: In a paramagnetic material, the atomic dipoles align along the applied magnetic field. Thus the resulting field is more than the applied field. So the magnetization will increase if the magnetic field is increased. Statement A is correct.  

    When the temperature is increased, the randomization of the individual atomic magnetic moments increases, thus decreasing the magnetization I for a given magnetic intensity. So the statement B is false. 

               Hence the option (b) is correct.     





    2.  A paramagnetic material is kept in a magnetic field. The field is increased till the magnetization becomes constant. If the temperature is now decreased, the magnetization 

(a) will increase

(b) decrease

(c) remain constant

(d) may increase or decrease.     


ANSWER: (c)   


EXPLANATION: When the temperature is decreased after the magnetization is constant, the alignment of individual magnetic dipoles does not vary. So the magnetization remains constant. Option (c) is correct.   




    3.  A ferromagnetic material is placed in an external magnetic field. The magnetic domains 

(a) increase in size

(b) decrease in size

(c) may increase and decrease in size

(d) have no relation with the field.   


ANSWER: (c)   


EXPLANATION: The magnetic domains inside a ferromagnetic material have the directions of magnetic moment randomly organized. When the ferromagnetic material is placed in an external magnetic field, the domains having the magnetic field direction along the external magnetic field direction, grow in size while those opposing it get reduced. Hence the option (c) is correct.        




    4.  A long straight wire carries a current 'i'. The magnetizing field intensity H is measured at a point P close to the wire. A long cylindrical iron rod is brought close to the wire so that point P is at the center of the rod. The value of H at P will 

(a) increase many times

(b) decrease many times

(c) remain almost constant

(d) become zero.    


ANSWER: (c)   


EXPLANATION: Since the cylindrical rod is long, end effects at the center of the rod may be neglected. So the magnetic intensity due to magnetization is zero. Thus the magnetizing field intensity is determined by the external sources only that is the current-carrying wire here. So H will remain almost constant at point P. Option (c) is correct.  




    5.  The magnetic susceptibility is negative for 

(a) paramagnetic materials only 

(b) diamagnetic materials only

(c) ferromagnetic materials only

(d) paramagnetic and ferromagnetic materials.  


ANSWER: (b)   


EXPLANATION: The intensity of magnetization I is proportional to magnetic intensity H. Thus,  

I = χH

   The proportionality constant χ is called the magnetic susceptibility of the material. It is positive for paramagnetic and ferromagnetic materials but negative for diamagnetic materials. Option (b) is correct.   




    6.  The desirable properties for making permanent magnets are  

(a) High retentivity and high coercive force

(b) high retentivity and low coercive force

(c) low retentivity and high coercive force

(d) low retentivity and low coercive force.    


ANSWER: (a)   


EXPLANATION: Permanent magnets have high magnetization even without the external magnetic field. To make a permanent magnet the material should have high retentivity. i.e. even when the external magnetizing field is brought back to zero, the material still remains magnetized. 

     Also, this residual magnetization should not be easily lost when the opposite magnetizing field is encountered. i.e. the value of H needed to dis-align the domains forcibly (coercive force) should also be high. Option (a) is correct.   




    7.  Electromagnets are made of iron because soft iron has 

(a) high retentivity and high coercive force    

(b) high retentivity and low coercive force

(c) low retentivity and high coercive force

(d) low retentivity and low coercive force.   

ANSWER: (d)   


EXPLANATION: Electromagnets need instant magnetization and instant demagnetization. For this, there should be very little magnetization left in the iron when the current is made zero. Also whatever magnetization is remained should get removed with little coercive force. So low retentivity and low coercive force, that is available in soft iron. Option (d) is correct.    

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Links to the Chapters





CHAPTER- 34- Magnetic Field

CHAPTER- 29- Electric Field and Potential











CHAPTER- 28- Heat Transfer

OBJECTIVE -I







EXERCISES - Q51 to Q55


CHAPTER- 27-Specific Heat Capacities of Gases

CHAPTER- 26-Laws of Thermodynamics


CHAPTER- 25-CALORIMETRY

Questions for Short Answer

OBJECTIVE-I

OBJECTIVE-II


EXERCISES - Q-11 to Q-18


CHAPTER- 24-Kinetic Theory of Gases







CHAPTER- 23 - Heat and Temperature






CHAPTER- 17 - Light Waves




CHAPTER- 14 - Fluid Mechanics



CHAPTER- 13 - Fluid Mechanics


CHAPTER- 12 - Simple Harmonic Motion








CHAPTER- 11 - Gravitation




CHAPTER- 10 - Rotational Mechanics




CHAPTER- 9 - Center of Mass, Linear Momentum, Collision


CHAPTER- 8 - Work and Energy

Click here for → Question for Short Answers

Click here for → OBJECTIVE-I

Click here for → OBJECTIVE-II

Click here for → Exercises (1-10)

Click here for → Exercises (11-20)

Click here for → Exercises (21-30)

Click here for → Exercises (31-42)

Click here for → Exercise(43-54)

CHAPTER- 7 - Circular Motion

Click here for → Questions for Short Answer 

Click here for → OBJECTIVE-I

Click here for → OBJECTIVE-II

Click here for → EXERCISES (1-10)

Click here for → EXERCISES (11-20)

Click here for → EXERCISES (21-30)

CHAPTER- 6 - Friction

Click here for → Questions for Short Answer

Click here for → OBJECTIVE-I

Click here for → Friction - OBJECTIVE-II

Click here for → EXERCISES (1-10)

Click here for → Exercises (11-20)

Click here for → EXERCISES (21-31)

For more practice on problems on friction solve these- "New Questions on Friction".

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CHAPTER- 5 - Newton's Laws of Motion


Click here for → QUESTIONS FOR SHORT ANSWER

Click here for→Newton's Laws of Motion,Exercises(Q.No. 13 to 27)

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CHAPTER- 4 - The Forces

The Forces-

"Questions for short Answers"    


Click here for "The Forces" - OBJECTIVE-I


Click here for "The Forces" - OBJECTIVE-II


Click here for "The Forces" - Exercises


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CHAPTER- 3 - Kinematics - Rest and Motion

Click here for "Questions for short Answers"


Click here for "OBJECTIVE-I"


Click here for EXERCISES (Question number 1 to 10)


Click here for EXERCISES (Question number 11 to 20)


Click here for EXERCISES (Question number 21 to 30)


Click here for EXERCISES (Question number 31 to 40)


Click here for EXERCISES (Question number 41 to 52)


CHAPTER- 2 - "Physics and Mathematics"

Click here for "Questions for Short Answers"


Click here for "OBJECTIVE-II"

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