Question

A metallic particle with no net charge is placed near a finite metal plate carrying a positive charge. The electric force on the particle will be
(a) towards the plate
(b) away from the plate
(c) parallel to the plate
(d) zero

Answer 1

(a) towards the plate

The particle is a conductor. When it is brought near a positively charged metal plate, opposite charge is induced on its face nearer to the plate, i.e. negative and the same amount of charge, but of opposite polarity, goes to the farther end, i.e. positive.
Now, the attractive force is due to charges of opposite polarity. As they are at a lesser distance than the same polarity charges, the force of attraction is greater than the force of repulsion. In other words, the force on the particle is towards the plate.