O-LevelPhysicsElectricity5054/21 · Oct/Nov 2025 · Q78 Marks

An insulating rod is made of plastic and is initially uncharged. The rod is rubbed with a cloth and becomes negatively charged.

(a)Describe, in terms of particles, what happens as the rod becomes negatively charged.[2]
(b)(i)Explain, in terms of particles, how an electrical conductor differs from an electrical insulator.[1]
(b)(ii)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 brought close to the ball.[3]
(b)(iii)Explain why the resultant force on the ball is towards the rod.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.

[C1] electrons mentioned or movement of negative charge mentioned
[A1] electrons move (from cloth) to rod
[B1] (in conductors) electrons are free to move
[B1] like charges repel
[B1] negative charges/electrons move away from the rod / to the right
[B1] positive charges/protons do not move or left-hand side (of ball) becomes positively charged
[B1] unlike/opposite charges attract
[B1] attractive force stronger (than repulsive force on negative charges)/positive charges closer to the rod.

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.