Explain the charging by induction in terms of movement of electrons.

Suppose we want to charge a metal rod A negatively by induction. Bring a positively charged glass rod B near one end of rod A.

The near end P of the rod A acquires negative charge and the far end Q acquires positive charge. The positively charged glass rod B attracts the free electrons from the end Q towards the end P of rod A. Thus, end P becomes negatively charged as it gains the electrons and end Q becomes positively charged as it loses the electrons.

Now touch the end Q of rod A by hand and then remove hand and rod B simultaneously. The rod A becomes negatively charged.

On touching the end Q of rod A, the free electrons move from earth to neutralize the positive charge at end Q. On removal of glass rod B and hand simultaneously, the negative charge at the end P gets distributed throughout the rod A making it negatively charged.