Static electricity and charge Cambridge IGCSE Physics (9–1) revision
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In plain words
Rub a balloon on your jumper and it sticks to the wall. Rubbing moves electrons from one thing to the other. The one that gains electrons becomes negative; the one that loses them becomes positive. Like charges push apart, and opposite charges pull together.
Three things to know
- There are two kinds of charge, positive and negative. Like charges repel; unlike charges attract.
- Rubbing two insulators together transfers electrons. The one that gains electrons becomes negative; the one that loses them becomes positive.
- Conductors (metals) let charge flow because they have free electrons; insulators (plastic, rubber, glass) do not.
Tips and tricks
- Only electrons move. Never write that positive charges or protons moved.
- Explain "becomes positive" as "has lost electrons", not as "gained positive charge".
It lands in your notebook with its questions as flashcards.
Static electricity and charge: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is transferred when an insulator is charged by rubbing?
Only electrons move; protons stay in the nucleus.
Two objects with the same kind of charge are brought close. What happens?
Like charges repel.
A rod gains electrons. What is its charge?
Electrons are negative, so extra electrons make it negative.
Which is a good electrical insulator?
Plastic has no free electrons to carry charge.
What is the unit of electric charge?
Charge is measured in coulombs.
Why are metals good conductors of electricity?
Free electrons can move through the metal and carry charge.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
4 questions, 7 marks. Write your answers on paper, then check them.
Static electricity and charge
Cambridge IGCSE Physics (9–1) 0972 · 7 marks · papermunch.org
Name ______________________________ Date ______________
A polythene rod is rubbed with a cloth and becomes negatively charged. Explain how.[2]
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Electrons are transferred from the cloth to the rod by friction.
In the question above, state the charge left on the cloth.[1]
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Positive (equal in size to the charge on the rod).
Explain why a charged balloon sticks to a wall.[2]
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It repels electrons in the wall's surface, leaving the surface nearest the balloon positive, which attracts the negative balloon.
Explain why a metal rod held in the hand cannot be charged by rubbing.[2]
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Metal is a conductor, so the charge flows through the rod and the person to earth.
Answers: Static electricity and charge
- 1. Electrons are transferred from the cloth to the rod by friction.
- 2. Positive (equal in size to the charge on the rod).
- 3. It repels electrons in the wall's surface, leaving the surface nearest the balloon positive, which attracts the negative balloon.
- 4. Metal is a conductor, so the charge flows through the rod and the person to earth.