Once charged objects exist, they exert forces on each other. The rule is simple:
- Like charges repel — two positive objects push each other apart; two negative objects push each other apart
- Unlike charges attract — a positive and a negative object pull towards each other
This is why a charged balloon sticks to a wall. The charged balloon repels electrons in the surface of the wall, leaving a region of positive charge near the balloon's surface. The negative balloon is attracted to the positive region — and sticks. This is called electrostatic induction.
Quick Check: A polythene rod is rubbed with a cloth. The rod becomes negatively charged. What charge does the cloth have, and why?
The cloth becomes positively charged. When the rod gains electrons from the cloth, the cloth loses those electrons. Since it now has fewer electrons than protons, it has a net positive charge. Total charge is conserved.
This deep dive covers Attraction and Repulsion Between Charges within Static Electricity for GCSE Physics. Revise Static Electricity in Electricity for GCSE Physics with 15 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 3 of 15 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Static Electricity
When a plastic rod is rubbed with a cloth, the rod becomes negatively charged. Which statement best explains why?
Explain why a fuel tanker must be earthed before fuel is pumped, and describe how earthing prevents a dangerous spark.