Magnetism

Magnets I.Magnetic Poles A.Magnets exert forces on one another 1.Similar to electric charges, they can attract and repel each other without touching 2.Strength of force dependent on distance between 2 magnets 3.Magnetic poles are regions of magnet that produce magnetic forces

A. Magnets exert forces on one another (continued) 4.Magnets hung from a string will act like a compass a.The end that points north is called the north- seeking pole (North) b.The end that points south is called the south- seeking pole (South) 5.All magnets have both a south and north pole at opposite ends

A. Magnets exert forces on one another (continued) 6.when the north pole of one magnet is brought near the north pole of another magnet they repel -The same is true of 2 south poles 7. Like poles repel; opposites attract

A. Magnets exert forces on one another (continued) 8.Magnetic poles can never be separated a.If you were to break a magnet in half, you would have two magnets

II. Magnetic Fields A.Definition 1.The region around a magnet, in which a magnetic force is exerted B.Magnetic Field lines 1.Drawn to indicate the shape of the field 2.Field lines are drawn from north pole to the south 3.Magnetic field is strongest where the lines are drawn closest together.

B. Magnetic Field lines (continued)

C. Nature of a Magnetic Field 1.Magnetic fields are caused by charges in motion (movement of electrons in an atom) a.Electrons spin like tops in an atom and produce a small magnetic field b.Each electron act like a small magnet - a pair of electrons in an atom with like spins create a stronger magnet (which is predominant in atoms of iron, nickel, and cobalt)

C. Nature of a Magnetic Field (c0ntinued) 2.Magnetic Domains a. The magnetic fields of individual iron atoms causes neighboring atoms to align their magnetic fields b. the clusters of atoms with aligned magnetic fields are called Magnetic Domains

C. Nature of a Magnetic Field (c0ntinued) 2.Magnetic Domains (continued) c. Domains are perfectly magnetized d. Unmagnetized iron contains magnetic domains that are randomly oriented

C. Nature of a Magnetic Field (c0ntinued) e. Magnetized materials contain aligned domains

D. Electric Currents and Magnetic Fields 1.Moving charges produce a magnetic field 2.A wire carrying an electric current produces a magnetic field in a concentric circle pattern

D. Electric Currents and Magnetic Fields (continued) 3.Right hand rule a.Used to determine the direction of the magnetic field around a wire b.Thumb points in direction of conventional current ( + to - ) a.Fingers wrap around the wire in the direction of the magnetic field

D. Electric Currents and Magnetic Fields (continued) 4.Field in a coil of wire a. Use right hand rule to determine direction of field b. Doubling the number of coils in the wire doubles the strength of the field.