Methods of demagnetization, Right hand grip rule
Methods
Heating
When heated with Bunsen burner, the atoms of the magnet will vibrate vigorously and cause the magnetic domains to lose their alignment. Letting the magnet cool in the East−West direction will ensure that the domains will not realign.
Hammering
Hammering a magnet in the East−West direction alters the alignment of the magnetic domains and causes the magnet to lose its magnetism.
Electrical Method using an Alternative Current (a.c)
Procedure:
- Connect the solenoid to an alternating current (a.c) supply.
- Place the magnet inside the solenoid
- Switch on a.c supply
- Slowly withdraw the magnet in East-West direction until it is some distance away from the solenoid while a.c current is still on.
Right Hand Grip Rule
Right hand grip rule is used to determine the pole of a permanent magnet produced using electrical method.
Thumb represents the North pole of a magnet;
Curling fingers represents the direction of current flow.
How?
Step 1: Grip the solenoid with right hand such that the fingers are
curled in the direction of current flow.
Step 2: The thumb represents the North pole of a magnet.
Current carrying loop in uniform magnetic field
In chapter 1, Electric charges and fields, we studied about current carrying circular conductor
The current carrying circular loop of N turns is analogous to magnetic dipole. In a current carrying loop, if we view from one side, say right side, the current appears to move in clockwise direction. This is like South polarity. If we view it from the other side, say left side, the current appears to move in the anticlockwise direction which is like North polarity.
This is similar to a rectangular loop below
