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On the syllabus: GCSE PhysicsA-Level Physics
Rub a balloon on your hair and hold it near a thin stream of water from a tap. The water bends toward the balloon — without touching it. No magnets, no wind, no strings. How can a piece of rubber reach out through the air and physically pull water?
Rub a balloon on your hair and hold it near a thin stream of water from a tap. The water bends toward the balloon — without touching it. No magnets, no wind, no strings. How can a piece of rubber reach out through the air and physically pull water?
Shuffling across carpet or rubbing a balloon transfers electrons — particles of charge — from one object to another. The balloon becomes negatively charged; it attracts the positive charges in water, bending the stream toward it. That invisible force is electrostatics, and it's the same physics behind lightning, chemical bonds, and every electronic device you've ever touched.
Electric charge (measured in Coulombs) is a fundamental property of matter. Like charges repel; unlike charges attract. The force between two charges follows Coulomb's Law: it grows with charge magnitude and shrinks with the square of distance.
Coulomb's constant k is enormous (9 billion) because the electromagnetic force is intrinsically strong — about 10³⁶ times stronger than gravity between the same two protons. The inverse-square dependence (1/r²) means doubling the distance quarters the force. This is the same geometric reason light from a lamp gets dimmer with distance. Electric field lines point from positive to negative and never cross. Their density indicates field strength.