electric fan

A metallic fan operated by an electric motor, and used for ventilating purposes. electric-field, s. The region of electrostatic in fluence surrounding a body charged with electricity, electric-flyer, s. A wheel so arranged as to be set in rotation by the escape of static electricity from its points when connected with a charged conductor. electric-fog, s. A dense fog which sometimes occurs when the atmosphere is surcharged with electricity. IMG:content-0831.png:[blocks in formation] match, all we do is to heat the gas up to this point. But we may light it just as well by any other means that will give the required heat. A picce of redhot wire will do it. An electric spark does it. There is very little heat in the spark itself, but very little is needed. It is degree of heat required, not quantity. If one tiny particle of hydrogen can be made hot enough to unite with oxygen, it will heat up its neighboring particles and spread the flame in an instant. To understand why the spark coil makes a spark we must remember i remember its construction. We have several pounds of wire, that is, several hundred feet, wound around a soft iron core When a current pa es through the wire, the core becomes a strong magnet. When the current is broken, the core ceases to be a magnet. At the same instant a strong current is momentarily induced in the coil. It is known as the "extra current," and is strong enough to jump through the air between the two little wires over the gas-burner, thus making a spark and lighting the gas. A current of electricity is always induced in a wire when it is near a changing magnet, or near another wire in which a current is made or broken. The extra current in the spark coil is due to both of these causes; the magnetism of the core changes, and the retreat of the original current along the turns of the coil induces secondary currents in the neighboring turns. Without the spark coil there would be no extra current, and consequently no spark.