17. Summary

Ohm’s law says voltage acts as a kind of potential energy that will cause charge to flow if there is a path (a circuit). The number of charges in a circuit remain fixed but they carry electrical energy which is turned into other useful forms of energy (light, heat, sound, etc.) by components in the circuit (light bulb, toaster, stereo). Currents cause magnetic fields. If a current finds itself in a magnetic field caused by some other source (magnet or other current) it will feel a force unless it moves parallel to the magnetic field. This is the basis of an electric motor. Faraday’s law says a¬†changing¬†magnetic field through an area (or equivalently, a changing area with constant field) will cause a voltage. This is the mechanism behind electric generators, credit cards, metal detectors, computer hard drives, etc.

End of chapter exercises:

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