Coulomb's Law
Place charges, see forces.
You rub a balloon on your hair, giving it a negative charge. You slowly bring the balloon toward tiny pieces of paper sitting on a table. The paper pieces are completely NEUTRAL — they have no net charge at all.
What happens to the paper pieces?
The paper jumps up and clings to the balloon! Even though the paper has zero net charge, the balloon’s electric field pushes electrons in the paper to one side, creating an induced dipole. The closer side (opposite charge) is attracted more strongly than the far side is repelled — so the paper leaps off the table.
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Place positive and negative charges on the canvas and watch the force arrows. Bring a charged object near a neutral one to see polarization in action — the charges inside rearrange!
F = kq₁q₂ / r²
Like charges repel, opposite charges attract. The force weakens with the square of distance — move twice as far away, the force drops to ¼.
Charge separation in storm clouds creates enormous electric forces. When the field exceeds air’s breakdown strength (~3 MV/m), a lightning bolt bridges the gap.
Accumulates charge on a metal dome until hairs stand on end and sparks fly — like charges on your hair repel each other, making every strand flee its neighbor.
A laser writes a charge pattern on a drum. Toner particles (charged powder) stick to the pattern by Coulomb attraction, then transfer to paper. Every printed page is Coulomb’s law at work.
Power plants use charged plates to attract soot and pollution particles out of exhaust gas — cleaning the air with electric force.
“Two charges, a distance, and an inverse square. That’s the law that holds atoms together, drives lightning, and makes your hair stick to a balloon.”
Charge Sandbox
Place positive and negative charges anywhere on the canvas. Watch the forces, field lines, and electric potential update in real time. Build dipoles, quadrupoles, or your own charge configurations — and see how the inverse-square law shapes everything.
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Start with two equal and opposite charges (a dipole). Watch the field lines arc from + to −. Now move them closer — the forces skyrocket. Try adding a third charge nearby and watch the whole field rearrange. Place a neutral test charge between two like charges — can you find the equilibrium point where the net force is zero?
Coulomb’s law is an inverse-square law, just like gravity. But unlike gravity, charges come in two signs — positive and negative — so the electric force can attract or repel. This single equation governs everything from atomic structure to lightning bolts.