# Basic Concepts of Magnetism – Short Questions Collection With Answer | Physics Class 12

## Very Important Questions Collection HSEB | Science Faculty Basic Concepts of Magnetism – Physics Grade XII Short Questions with Answer (Solution)

1. Define the terms :
(a) Magnetic field : The space around a magnet in which its magnetic effect can be experienced is called magnetic field. A magnetic field exists at point if it can exert a force on moving charge.its unit is Tesla(T).

(b) Magnetic dipole : An arrangement of two magnetic poles of equal and opposite strength separated by a finite distance is called magnetic dipole.

(c) Magnetic dipole moment (M) : The product of strength of either pole and the magnetic length of magnet is called magnetic dipole moment. It is vector quantity and represented by M. M = m x 2I, where ‘m’ is magnetic pole strength of the magnet.

2. Can magnetic lines of force intersect? Explain.
Ans. The direction of tangent to a point on a magnetic line of fore gives the direction of the magnetic field at that point. If two lines of force could intersect at a point, there could be two tangents at the same point showing two different directions of the magnetic field at the same point. More than one directions of the magnetic field at a point is impossible. Hence, magnetic line of force cannot intersect.

3. What are the basic difference between electric line of force and magnetic lines of force?
Ans. The difference between magnetic and electric lines of force are as shown in below table:

 Magnetic Lines of Force Electric Lines of Force a. They emit from N pole and terminate at S pole outside the magnet but S pole to N pole inside the magnet. a. They start from positive charge and end into negative charge. b. They are closed loops i.e. they lie inside and outside the magnets. b. They are unclosed loops i.e. they lie outside the charged conductor only. c. They are not produced being normal to the surface of magnet c. They are produced being normal to the surface of charged conductor. d. The tangent drawn at any point on the magnetic line of force gives the direction of magnetic field intensity. d. The tangent drawn at any point on the electric line of force gives the direction of electric field intensity.

4. What do you mean by magnetic field intensity and intensity of magnetization?
Ans. Magnetic field intensity: The magnetic field intensity at a point is the force experienced by a unit North Pole at that point. The tangent, which is drawn on the line of forces, gives the direction of magnetic field intensity. It measures in Telsa(T) or Gauss.

Intensity of magnetization:  The ratio of sum of all magnetic moments of the substance to the volume of substance is called intensity of magnetization.

5. Define the terms:
Ans. (a) Magnetic meridian: Earth behaves as a huge magnet. The axis of huge magnet assumed to lying inside the earth is called magnetic axis. A vertical plane passing through the magnetic axis of earth is called magnetic meridian.
(b) Angle of dip: The angle between the direction of the total intensity of earth’s magnetic field and a horizontal line in the magnetic meridian is called angle of dip at a place.
(c) Angle of declination: The angle between the magnetic meridian at a place and the geographical meridian at that place is called angle of declination. It is different at different places on surface of earth.

6. What is tangent law? Ans. If a small bar magnet is suspended in two mutually perpendicular uniform magnetic fields vector B and vector BH, such that it comes to rest making an angle o with the direction of fields vector BH.Then, vector B = vector BHtanƟ. This is tangent law.

7. What is an angle of dip? How does it vary from equators to pole? Ans. The angle between the direction of the total intensity of earth’s magnetic field and a horizontal line in the magnetic meridian is called angle of dip at a place. At equator, the value of angle o dip is zero and the angle of dip at poles is 90 degree.Thus value of angle of dip increases from equator(where it value is 90°) to poles.

8. Can a deflection magnetometer be used at the earth’s magnetic poles? Explain.
Ans. No, the deflection magnetometer works with the help horizontal component of earth’s magnetic field. But there is no horizontal component of earth’s magnetic field at pole. Therefore, at the poles, the deflection magnetometer cannot use at the earth’s magnetic poles.

9. At a neutral point, a magnetic or compass needle is unable to show proper direction, why?
Ans. A neutral point is the point where the field due to magnet is completely neutralized by the horizontal component of earth’s magnetic field. Therefore, there is no net force to influence a magnetic needle kept there.Hence, the magnetic needle is unable to show proper direction at neutral point.

10.What is difference between deflection magnetometer and a vibration magnetometer?
Ans. The vibration magnetometer works under the principle of simple harmonic motion, whereas, the deflection magnetometer works under the principle of tangent law. so, two perpendicular tangent fields are needed in a deflection magnetometer, while a single uniform field is in an oscillation magnetometer.

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