lesson
Charges can exert forces without contact
1 · Learn
Rubbing suitable insulating materials can transfer electrons, leaving one object with extra electrons and the other with a deficit. Like charges repel and unlike charges attract. The total charge is conserved across the transfer.
An electric field describes how a charge would experience force in a region. A static-charge model is not an excuse to experiment with high voltage or electronic equipment that can be damaged by discharge.
2 · Worked example
If electrons move from A to B, A becomes positively charged relative to its neutral state and B negatively charged. Positive charge here does not mean protons moved between the objects.
3 · Your turn
Which particles are described as transferring in the rubbing model?
Check your answer
Electrons; do not infer that protons move from one solid object to the other in this model.
4 · Apply your learning
Use diagrams or an approved simulation to track charge before and after transfer and explain the resulting force direction.
Adult guidance and safety
Use supplied evidence and approved diagrams. Practical work requires a qualified adult, suitable equipment and a risk assessment. No unsupervised chemicals, heating, flames, mains electricity or bright-light experiments. Human biology is factual education, not personalised medical advice; never request intimate or health disclosures.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
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