Electro-magnetic Extravaganza
by Cameron Cummings and Sadey Nevin
Electromagnetic Induction in Motors and Generators
Improving Lives
Microwave
A microwave uses electric forces by generating a micro-wave with a frequency of about 2.4 GHz. These waves excite the atoms in the food and force them to shake rapidly, heating the food. It is very efficient as a heating device because this unique wavelength only causes water molecules to shake, so energy does not get wasted heating solids such as glass.
Credit Card Reader
A credit card has a magnetic strip that has millions of tiny pieces of iron about 20 millionths of an inch long. These strips store data using magnetic fields to line up the pieces of iron. This is very similar to how cassette tapes work.
Hard Drive
A hard drive is another example of where electric fields and forces meet magnetic fields and forces. A hard drive has several platters with that are precision coated with magnetic material. This material is magnetized when a motor spins the disks and the read/write heads move over the platter. The heads remagnetize that particular section of the platter to store information.
Microphone
A microphone is a transducer; it changes information from one form to another. In the magneto-dynamic microphone, sound waves cause movement of a thin metallic diaphragm and an attached coil of wire. A magnet produces a magnetic field surrounding the coil, and the motion of the coil within this field causes the current to flow. The motion of the diaphragm produces the current, and the amount of current is determined by the speed of that motion.
VHS Tapes
The recordings on VHS tapes are electromagnets that draw particles of metal onto the tape in patterns set by TV signals. In order to record onto a VHS tape, it must be attached to the TV signal. As the tape passes the recording heads, the signals are recorded from the electrical signal onto each of the heads of tape.
Speakers
Speakers use electromagnetic induction to produce sound. In order to translate an electrical signal into an audible sound, speakers contain an electromagnet: a metal coil, which creates a magnetic field when an electric current flows through it. The coil reverses the direction of the current and flips the poles of the magnet. Inside speakers, an electromagnet is places in front of a magnet. The magnet is fixed in a position where the electromagnet is mobile. As electricity moves through the electromagnet, the direction of its magnetic force changes. This means that it switches from being attracted to, and repelled from, the fixed magnet, which makes it vibrate. The vibrations govern the pitch of the sound and their amplitude affects the volume.