A student rubs a woollen jumper against a balloon. The balloon is then held close to, but not touching, small pieces of tissue paper on a table. The pieces of tissue paper are attracted towards the balloon. Explain why the tissue paper is attracted to the balloon.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Rubbing transfers electrons from the woollen jumper to the balloon, giving the balloon a negative charge.
The negative charge on the balloon repels the electrons in the tissue paper, so the electrons move away from the surface nearest the balloon.
This leaves the surface of the tissue paper nearest the balloon with a net positive charge.
The opposite charges attract, so the positively charged surface of the tissue paper is attracted to the negatively charged balloon.
The negative charge on the balloon repels the electrons in the tissue paper, so the electrons move away from the surface nearest the balloon.
This leaves the surface of the tissue paper nearest the balloon with a net positive charge.
The opposite charges attract, so the positively charged surface of the tissue paper is attracted to the negatively charged balloon.
Examiner tips
- Use the word "repels" for like charges and "attracts" for unlike charges. Mention that electrons move away, leaving a positive surface. Show the sequence: transfer → repulsion → separation → attraction.
Common mistakes
- Saying the balloon becomes positively charged. Forgetting to explain that electrons move away from the balloon. Using vague terms like "electrical force" without specifying charge types.
Mark scheme (4 marks)
- Rubbing transfers electrons from the woollen jumper to the balloon, giving the balloon a negative (static) charge.
- The negative charge on the balloon repels negative charges (electrons) in the tissue paper, so they move away from the surface closest to the balloon.
- This leaves the surface of the tissue paper closest to the balloon with a positive charge (net positive charge on that side).
- The unlike/opposite charges attract, so the positively charged surface of the tissue paper is attracted to the negatively charged balloon.
Related
- All Pearson Edexcel International GCSE Physics (4PH1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →