Question

what is right hand thumb rule ?

Answer 1

It shows the direction of induced current when the conductor is moved in a magnetic field.
In this rule, right hand having, thumb, fore finger and middle finger take part. and all are perpendicular to each other.
Thumb shows the direction of motion of conductor.
Fore finger shows the direction of magnetic field
Middle finger shows the direction of induced current.

Answer 2

If we hold the current carrying conductor in right hand in such a way that our thumb points in the direction of current, then the other 4 fingers encircle the wire in the direction of the magnetic field lines