An insulating rod is plastic and is uncharged at the start. It is rubbed with a cloth, after which it acquires a negative charge. A light ball has a thin conducting surface and hangs from the ceiling on an insulating thread. The ball has no charge. When the negatively charged rod is moved close to the ball, Fig. 7.1 shows the ball being pulled towards the rod by a force. Diagram labels: ceiling, insulating thread, light ball, negatively charged rod, direction of force.
(a)[2]
Describe, in terms of particles, what occurs as the rod becomes negatively charged.
(b(i))[1]
Explain, in terms of particles, how an electrical conductor is different from an electrical insulator.
(b(ii))[3]
The conducting surface of the ball contains both negatively charged particles and positively charged particles. Explain what happens to the negatively charged particles and to the positively charged particles as the rod is moved close to the ball.
(b(iii))[2]
Explain why the resultant force on the ball acts towards the rod.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “A mention of electrons or movement of negative charge” …