Magnetism and Electromagnetictism
Featuring: Faraday & Tesla • Nick Marietta & Katie Blanks
Electromagnetic Induction
Michael Faraday
If Electricity can create Magnetism...
http://www.ilt.columbia.edu/projects/bluetelephone/html/faraday.html
Nikola Tesla
Magnetism in the Real World
Magnetism is used in every day devices to make life easier, safer, and more advanced. We use magnets to find our way, to pick up scrap metal with cranes, and even to watch movies.
Department Store Security Devices
A burglar alarm consists of a contact switch, which responds to changes in the environment and sends a signal to a noise making device. The contact switch, a permanent magnet, is installed in the frame of a window or door, and a piece of magnetized material in the window or door itself. Once the alarm is activated, it will respond to any change in the magnetic field. So, when someone slides open the door or window, they break the magnetism and set off the alarm.
The MRI
The MRI machine is activated after a large tube is placed in the patient. A technician then activates a powerful magnetic field, which causes atoms within the patient's body to spin at precise frequencies. The machine then beams radio signals at a frequency matching that of the atoms in the cells (e.g., cancer cells) being sought. Upon shutting off the radio signals and magnetic field, those atoms emit bursts of energy that they have absorbed from the radio waves. At that point a computer scans the body for frequencies matching specific types of atoms, and translates these into three-dimensional images for diagnosis.
The Microphone
A microphone contains a capacitor, a system for storing charges in the form of an electrical field. The capacitor's negatively charged plate constitutes the microphone's diaphragm, which, when it is hit by sound waves, vibrates at the same frequency as those waves. Current flows back and forth between the diaphragm and the positive plate of the capacitor. This in turn produces an alternating current, at the same frequency as the sound waves, which travels through a mixer and then an amplifier to the speaker.
The Compass
A magnetic compass works because Earth itself is like a giant bar magnet. Known as the geomagnetic field, the source of Earths magnetism is a core of molten iron which runs over half of the Earths diameter. Within this core run powerful electric currents that ultimately create the geomagnetic field. When a magnetized strip is hung from a string it always lines up with Earth's magnetic field, and points in a north-south direction.
The Loud Speaker
A loudspeaker typically contains a circular permanent magnet, which surrounds an electrical coil and is in turn attached to a cone-shaped diaphragm. Current enters the speaker ultimately from the microphone, alternating at the same frequency as the source of the sound (a singer's voice, for instance). As it enters the coil, this current induces an alternating magnetic field, which causes the coil to vibrate. This in turn vibrates the cone-shaped diaphragm, and reproduces sounds generated at the source.
Works Cited
"Magnetism: Real Life Applications."Science Clarified. N.p., n.d. Web. 25 Mar. 2013. <http://www.scienceclarified.com/everyday/Real-Life-Physics-Vol-3-Biology-Vol- 1/Magnetism-Real-life-applications.html>.
Wagon, Joy. "Electromagnetic Induction." Electromagnetic Induction. Science Joy Wagon, 1998. Web. 26 Mar. 2013.
<http://www.regentsprep.org/Regents/physics/phys03/dinduction/>.