CBSE Guess > Papers > Important Questions > Class XII > 2007 > Physics > Physics (Magnetism) By: Mr. Abhishek Gupta

Magnetism

Q. 1. Find the magnetic moment of a coil of area 2m2 and carrying a current of 5A.

Q. 2. Find the magnetic moment of a bar magnet of pole strength 10Am and length 5cm.

Q. 3. The magnet in the above question is placed in a uniform magnetic field of 2T. Find the torque experienced by it. What is the net force acting on the bar magnet?

Q. 4. A solenoid of length 2m has 2000 turns and carries a current of 10A. Find the magnetic field at its centre. What is the direction of this field.

Q. 5. Find the magnetic field at the corner of the solenoid in the above question

Q. 6. A bar magnet of moment 2Am² is cut along transverse to its length. Explain how the dipole moment will change.

Q. 7. A coil has an area of 4m² and has 100 turns. It is kept in a uniform magnetic field of 100G such that the plane of the coil makes an angle of 30o with the field lines. Find the torque experienced by it.

Q. 8. Explain why no work is done by the magnetic field on a moving charge particle.

Q. 9. An infinite wire carries a current of 4A in the South to North direction. Find the magnetic field at a point 5m to the east of this wire. Give the direction of the field.

Q. 10. A circular coil of radius 50cm has 10 turns and carries a current of 5mA. A soft iron piece of relative permeability 800 is kept inside it. Find the magnetic induction at its centre.

Q. 11. Define magnetic field and mention its unit.

Q. 12. An electron and a proton with equal momentum enter a magnetic field perpendicular to the field lines. What is the ratio of the radii of curvature of their trajectories?

Q. 13. Derive the force b/w 2 current carrying wires. Hence define an Ampere

Q. 14. A circular coil of radius 10cm has 100 turns and carries a current of 5A in the clockwise direction. The coil is placed in a uniform magnetic field of 10T. Find the torque that will act on the coil when the direction of magnetic field is

1. Parallel to the plane of the coil
2. Perpendicular to the plane of the coil.

Also find the net force acting on the coil in both cases.

Q. 15. The horizontal component of the earth's field at a place is 0.4G and the angle of dip is 60 degrees. Find the value of vertical component and the total intensity at that place.

Q. 16. Derive Curie’s law. What is curie temp?

Q. 17. Briefly explain all the elements of earth’s magnetism

Q. 18. At some place on earth the horizontal component of earth's magnetic field is 17.32G and the vertical component is 10G. Find the angle of dip and the resultant intensity

Q. 18. Draw magnetic field lines due to a bar magnet and a solenoid carrying current.

Q. 19. What are magnetic field lines? Give 2 properties. How do these lines differ from electric field lines?

Q. 20. What is Biot-Savart law? Using it derive the magnetic field intensity at the centre of a coil.

Q. 21. State Ampere’s law. Using it derive the magnetic field at the centre of a solenoid.

Q. 22. Mention 3 important difference b/w paramagnetic and diamagnetic substances giving 2 examples each.

Q. 23. A proton enters a magnetic field with a velocity of 50m/s perpendicular to the field lines. Find the radius of its path and time period of motion.

Q. 24. The radius of the Dees of a cyclotron is 2m and the magnetic induction is 4T. Find the maximum velocity and maximum kinetic energy that can be imparted to a proton using this cyclotron.

Q. 25. What is Hysterisis? Draw the hysterisis loops for soft iron and steel. Explain Retentivity and Coercivity. Hence explain which material would you prefer for making

1. Permanent magnet
2. Core of a transformer
3. Electromagnet

Q. 26. ; A moving coil galvanometer is made of a coil of radius 10cm and has 1000 turns. The strong horse shoe magnets create a magnetic field of 0.2T and the spring has a spring constant of 0.5 N/^om. Find

1. Galvanometer constant G
2. Current sensitivity I_s
3. Voltage Sensitivity V_s

Explain how a galvanometer can be made more sensitive

Q. 27. Explain the Construction and Working of a cyclotron. Mention 2 disadvantages.

OR

Q. 28. A particle of mass 50gm has a charge of 2mC. The region consists of a uniform magnetic field of 500G directed into the plane. The particle enters the region with a velocity of 250m/s towards north. Using a figure show the path of the particle and find the following

1. Force acting on the particle
2. Radius of its path
3. Time period of its motion
4. Frequency