Coulomb's Law
Part of the Electricity and Magnetism section of Coddy's Physics journey. Lesson 2 of 51.
Two charges a distance r apart push or pull each other with a force:
F = k q₁ q₂ / r²
k = 9 × 10⁹ N·m²/C². Use the sizes of the charges: the signs only give the direction (like repel, opposite attract).
Both charges feel forces of the same size, in opposite directions, along the line between them.
The distance is squared: twice as far apart, the force is four times smaller; twice the charge on one of them, twice the force.
Challenge
Two small charged spheres carry 2 μC and 3 μC, and their centres are 0.3 m apart. How big is the electric force F between them?
Try it yourself
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
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