a) TV Screen Activity :
- Take a bar magnet and bring it near the TV screen.
- Then the picture on the screen is distorted.
- Here the distortion is due to the motion of the electrons reacting the screen are affected by the magnetic field.
- Now move the bar magnet away from the screen.
- Then the picture on the screen stabilizes.
- This must be due to the fact that the magnetic field exerts a force on moving charges. This force is called magnetic force.
- The magnitude of the force is F = Bqv where B is magnetic induction, ‘q’ is the charge and v is the velocity of the charged particle.
b) Procedure :
- Take a bar magnet near to the TV screen. We observe that electrons are affected by the field produced by the bar magnet. Then the picture is disturbed.
- Move the bar magnet away from screen. Then you will get a clear picture.
- The force on the moving charge is given by F = Bqv.
- Right hand rule is used when velocity and field are perpendicular to each other.
Fore - finger ------> direction of current (V).
Middle - finger -------> direction of field
Thumb ------> direction of force
This rule is applicable to positive charge.