Chapter 1 · Physics
Electric Charge: Like Charges Repel, Unlike Attract
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Those sparks when you pull off a sweater come from electric charge. How rubbing moves electrons, what positive and negative mean, and why like charges repel.
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Key points
- Rubbing two bodies transfers electrons from one to the other.
- Charge is not created: the pair's total stays the same.
- The body that loses electrons becomes positive; the one that gains them becomes negative.
- Glass rubbed with silk is positive, and the silk negative. Plastic rubbed with fur is negative.
- Like charges repel, unlike charges attract.
What each rubbed object becomes
| Pair | Loses electrons (+) | Gains electrons (−) |
|---|---|---|
| Glass and silk | Glass | Silk |
| Plastic and fur | Fur | Plastic |
Try it yourself
Goal: See that rubbing only moves electrons, then predict which rubbed objects repel or attract.
- Choose a pair and press Rub once.
- Watch the two charges: the pair's total stays 0.
- Rub the other pair too.
- Pick two objects and predict: will they repel or attract?
Quick quiz
3 questions. Choose an answer for each, then submit to see your score and the explanations.
