Enamel-coated copper wire is covered with a polyurethane resin instead of plastic insulation. It is useful in electronics projects because the enamel coating acts as a flux in soldering, so you can use the wire immediately in building circuits without removing a coating.
Coated copper wire is used to make attractive jewellery and in sculpture projects. It also is necessary for making crystal radio sets and for electromagnetic learning activities.
Take a nail and wrap a few turns of enamel-coated copper wire around it, attach a battery to the ends and you made an electromagnet. It's in every electric motor, generator, and many electronics components.
Copper wire coils are part of an electrical device called an inductor. The principle of induction was first published by the British researcher Michael Faraday. The wire coil of an inductor can create electrical energy when a magnet is moved inside the coil. The motion of the magnet generates the current and if the magnet stops, the current stops. The principle of induction also makes cooper wire coils useful in communications technology.
The earliest forms of radio were crystal sets that used a copper wire coil, a capacitor as a tuner and a galena crystal as a receiver. These early AM radio sets revolutionised long-distance communications by allowing radio operators on ships at sea to send and receive messages to each other and the mainland. Radio quickly became the primary source for news and entertainment, with millions of crystal radio sets sold for home use.
Crystal radios, also called "cat's whisker" radios, pick up the radio signal with an antenna. The signal from the antenna causes an alternating current in the wire coil. The coil has little resistance to direct current passing through it, but the AM signal from the antenna creates alternating current and the coil resistance, or impedance, varies as the frequency of the signal varies. The combination of coil and resistor converts the radio waves to electrical signals and the sliding contact touches the coil at different points to tune in different frequencies. The electricity is passed through the end of the copper wire into the crystal, which rectifies it into signals the earphone speaker can reproduce as sound.
According to University of Virginia website How to Build Modern Versions of Early Speaking Telegraphs, you can use enamel-coated copper wire to recreate some of Alexander Graham Bell's experiments with speaking telegraphs. One interesting thing that you can make using copper wire is a replica of the Bell photophone transmitter. This 1881 invention could transmit the speaker's voice using a beam of light. Mr. Bell used selenium but you can use an inexpensive solar cell. For the experiment you connect a tin can with a mirror on the bottom. When you talk into the can, the light reflected from the mirror carries the signal to the small solar cell, which converts it into electrical energy. The electric energy flows through the enamel-coated copper wire, which is wrapped into a coil around a bolt to make a transformer. The energy continues on down the copper wire to the speaker and comes out as your voice.
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- SUNY College of Environmental Science and Forestry: How Does It Flow? Electricity, In Circuits, and Motors
- Florida State University: Faraday's Magnetic Field Induction Experiment
- University of Utah: Just for Fun---Crystal Radios
- University of Virginia: How to Build Modern Versions of Early Speaking Telegraphs
- Thomas Jefferson Lab National Accelerator Facility: How do I make an electromagnet?