How Do Bug Zappers Work?

Bug Zapper Structure

A bug zapper has a fluorescent bulb inside which emits ultraviolet and near ultraviolet light. Outside the light are two wire screens, one around the other. Around the electric screens is a protective cage to stop people from getting close enough to get a shock. When a bug flies between the wire screens, it gets zapped by a high voltage electric charge, instantly killing it.

Luring Them In

Because the flowers that attract many insects reflect a lot of ultraviolet light at night, many bugs are attracted to the UV light. The bug zapper also produces a fair bit of heat, which can attract certain other insects. The UV light itself will not harm bugs, but it will lure them toward the wire screens.

Powering the Screens

The electric screens themselves are powered by a high-voltage electric source such as a step-up transformer. When alternating coil runs through a coil, it creates a magnetic field. If another coil is near the primary coil, that field creates a current in the secondary coil. If there are more windings in the second coil, it will increase or step up the voltage. Depending on the design of the bug zapper, the transformer can produce 2,000 volts or more

Zapping Bugs

If two electrodes are separated by air, current will not normally flow between them. The air is an insulator -- a device that does not readily conduct electricity. If they have enough voltage or something lowers the voltage between the electrodes, however, a spark will jump from one to the other. The two wire meshes are electrodes separated by just enough air that they will not normally spark. The body of an insect is a good conductor, however. When an insect flies between the electrodes, a spark can jump from one electrode through the insect's body to the other. Even if the insect doesn't actually touch the electrodes, it can lower the resistance enough to make the spark jump. The spark is hot enough to literally cook the insect's body, instantly killing it.