Electric's Article

• Magnetic Poles
• –South Pole
• –North Pole
• –Magnetic lines of force exist between the north and south poles. Like poles repel. Opposite poles attract.
• –Each magnetic line of force is an independent line. None of the lines cross or touch a bordering line.
• •Natural Magnets: Lodestones were used by mariners for navigation.
• •The Earth is a large magnet surrounded by a magnetic field. (i.e. degaussing coils).
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• •Q. What are some uses for magnets?
• •A. Relays, Levetron, hold things in place.
• •Q. How can a magnet loose its magnetism?
• •A. Pounding or dropping magnets upsets the molecular alignment and weakens the magnet. Heat sources also destroy magnets by causing increased molecular activity, expansion and a return to the molecules random positions.
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• •Magnetic flux: The many invisible lines of magnetic force surrounding a magnet.
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•B=Φ/A

* B=Flux density in gauss (webers per square centimeter)

* Φ(phi)=Number of lines

* A=Cross sectional area in square centimeters

•3rd Law of Magnetism:

* The attractive force increases as the distance of the distance between the magnets decrease.

* Magnetic force varies inversely with (Distance)2

•Relay: Device used to control a large flow of current by means of a low voltage, low current circuit. A relay is a magnetic switch.

–Coil: Attracts armature because of magnetism.

–Armature: Lever Arm.

–Contacts: Normally open (NO) Normally closed (NC)

•Relay Maintenance:

–Burnishing tool cleans contacts

–Silver plated armatures should be replaced if there is exposed copper.

•HSST is a magnetic levitation transportation system that has been developed in Japan by HSST Development Corporation established in 1993.

•The HSST is magnetically-levitated (not supported by wheels) and is propelled by a linear induction motor (LIM), not by conventional rotary electric motors.

•Q. How does a relay work?

•A. Coil energizes, armature engages, secondary contact shuts/opens.

•Q. When would a use a magnetic circuit breaker?

•A. Used in electric plants to parallel generators and switchboards.

•Q. What is the LHR for conductors?

•A. Fingers: wrap around coil. Thumb: points in direction of current.