Magnetism

Chapter 9: Magnetism

__** Summary **__

Magnets are objects surrounded by a magnetic field, made up of lines of force called flux lines. They have two poles, north and south. As Coulomb's law states, like charges (poles) repel, and opposites attract. Flux lines cannot cross and tend to form the smallest possible loop. Current produces a magnetic field, whereas a magnetic field can induce current flow. As a conductor is coiled, the magnetic field is strengthened. This results in an electromagnet. Quantities such as permeability and reluctance are very important. There are many kinds of inductions, such as magnetic and electromagnetic.


 * __ Vocab __**

· Permanent magnet – retains magnetic field for long time · Temporary magnet – quickly loses magnetic field · Permeability – ease at which matter accepts lines of flux · Reluctance – opposition to flux · Flux density – # of flux lines per unit of area · Natural magnet – naturally surrounded by magnetic field · Artificial magnet – made from natural magnet · Residual magnetism – when magnet is removes, field remains · Retentivity – ability to retain magnetic field · Magnetic induction – inducing magnetic field into object without contact · Electromagnetic induction – EMF induced when moved across magnetic field · Left hand rule for conductor – grasp in left hand with thumb in direction of current flow. Fingers in direction of flux lines · Left hand rule for coil – grasp in left hand with fingers in direction of current flow. Thumb points towards north pole