SOME MAGNETIC RULES

1Q: What is cork screw rule?
Ans: If a right handed bottle-opener cork screw is assumed to be along the conductor so as to advance in the direction of current flow, the motion of its handle will indicate the direction of magnetic flux produced around the conductor.

2Q: What is right hand rule?
Ans: If a conductor is gripped by the right hand in such a way that the thumb remains in the direction of current flow then the fingers will represent the direction of magnetic flux produced around the conductor.

3Q: What type of magnetic field is formed by a current carrying conductor loop?
Ans: The magnetic field of a current carrying conductor loop is also composed of concentric lines of force, but in this case the lines of force get condensed inside the loop and rarified outside the loop.

4Q: What type of magnetic field is formed by a current carrying solenoid?
Ans: The magnetic field of a current carrying solenoid is identical to the magnetic field of a bar magnet. One end of the solenoid acts as north-pole and the other as south-pole.

5Q: What is end rule?
Ans: If on looking at any one end of  a solenoid, the direction of current flow is found to be clockwise then the end under observation is a south-pole.

6Q: What is Helix rule?
Ans: If a solenoid is gripped by the right hand with the fingers pointing the direction of current flow, the outstreched thumb will then point the north-pole.

7Q: What is permeability?
Ans: The magnetic flux density produced by a magnetising force in a substance in comparison to that produced in air or vacuum is called the permeability of that substance.

8Q: What are the types of magnetic materials?
Ans: There are three types of magnetic materials:
(1) Ferro -magnetic: materials having a permeability of 200 to 1000, e.g. iron, steel etc.
(2) Dia -magnetic: materials having a permeability of less than 1, e.g. antimony, bismuth etc.
(3) Para -magnetic: materials having a permeability of slightly greater than 1, e.g. copper, aluminium etc.

9Q: What is meant by magnetic induction?
Ans: When a magnet is brought near to an iron bar or when iron bar is brought near to a magnet, a magnetism is produced in the iron bar. The phenomenon is referred as magnetic induction.

10Q: What is meant by the intensity of magnetic field?
Ans: The force acting on a unit pole placed in a magnetic field is called the intensity of magnetic field. It is denoted by letter H and its unit is Wb/m. 

MAGNETISM

1Q: What is magnetism?
Ans: Magnetism is the property of certain materials of attracting small iron pieces towards them.

2Q: What is a magnet?
Ans: A magnet is a piece of iron or other magnetic material which can attract small iron pieces towards it.

3Q: What are the principle properties of a magnet?
Ans: (1) A freely suspended magnet always rests in north-south direction.
(2) Like poles of two magnets repel and unlike poles attract each other.
(3) Each magnet has two poles - North and South.

4Q: What is the molecular theory of magnetism?
Ans: Every molecule of a substance behaves like a tiny magnet because of its spin motion. It has a north and a south pole. When these tiny magnets are set in a definite linear order, the substance then starts to behave as a magnet.

5Q: What are the types of magnets?
Ans: Magnets are of two types - (1) Natural and (2) Artificial.

6Q: What are the types of artificial magnets?
Ans: There are two types of artificial magnets - (1) Permanent magnets and (2) Temporary magnets.

7Q: What materials are used for making permanent magnets?
Ans: Tungsten steel, cobalt steel, ALNICO or ALCONEX alloy are used for making permanent magnets.

8Q: What is meant by magnetic field?
Ans: A magnetic field is the space around a magnet in which the influence of the magnet can be detected.

9Q: What is meant by magnetic line of force?
Ans: A magnetic line of force is an imaginary closed curve which starts from north-pole and terminates at south-pole of the magnet. The curve completes its path through the magnet from south-pole to north-pole.

10Q: Can two lines of force intersect each other?
Ans: No, two lines of force can never intersect each other.

11Q: How does the direction of line of force determined?
Ans: A tangent drawn at any point on a line of force represents the direction of magnetic field acting at that point.

12Q: What is magnetic flux?
Ans: The bunch of magnetic lines of force is called magnetic flux. It is denoted by letter(phi) and its unit is weber.
1 Wb = 10^8 maxwells.

13Q: What is meant by magnetic flux-density?
Ans: The 'magnetic field strength' per unit area is called magnetic flux-density.

14Q: What is an electromagnet?
Ans: A soft iron bar when placed inside a direct current carrying coil acts like a magnet and it is called an electromagnet.

15Q: Is an electromagnet a permanent or temporary magnet?
Ans: An electromagnet is a temporary magnet and its magnetism lasts so long as the current is flowing through its coil.

16Q: What type of magnetic field is formed by a straight current carrying conductor?
Ans: The magnetic field of a straight current carrying conductor is composed of concentric magnetic lines of force.