Overvoltage

Similarly other electrical devices may stop working, or may even burst into flames if an overvoltage is delivered to the circuit.

Man-made sources of spikes are usually caused by electromagnetic induction when switching on or off inductive loads (such as electric motors or electromagnets), or by switching heavy resistive AC loads when zero-crossing circuitry is not used - anywhere a large change of current takes place.

A recent military development is that of the exploding capacitor designed to radiate a high voltage electromagnetic pulse.

If the generator speed increases suddenly, such as due to inadvertent throttle movement or unstable operation of the prime mover, this can cause brief but damaging overvoltage to any connected equipment.

Filters are used to prevent spikes entering or leaving the equipment through wires, and the devices coupled electromagnetically to space (such as radio-frequency pick-up coils in MRI scanners) are protected by shielding.