Magnetism Magnetism is a property of certain metals that is due to the orientation of atoms within the material.

Answer Me!!!  Magnets, how do they work?

Magnetic Field  A magnetic field is the region around a magnet that has a magnetic force.

Magnetic Field Lines  Magnetic Field Lines (also called Flux lines) represent the concentration of the magnetic field and point from the North to South pole.  Magnetic field lines follow the same rules as electric field lines

Practice Problem 1  If a compass is placed in the following magnetic field. Draw the orientation of the compass arrow.

Magnetic Field Strength  The closer the magnetic field (flux) lines, the stronger the magnetic force.  The number of magnetic field lines is measured in Webers.  Magnetic field strength is measured in Webers/m 2 called a Tesla.

Practice Problem 2 Where is the Magnetic Field Strength the greatest? A B C D A B C D

Answer Me!!!  A small object is dropped through a loop of wire connected to a sensitive ammeter on the edge of a table. A reading on the ammeter is most likely produced when the object falling through the loop is a Battery Bar magnet Brass mass Plastic ruler

Electromagnetic Induction  When a wire cuts across magnetic field lines, charges in the wire are force to move from one end of the wire to the other producing an electric potential difference across the wire.

Electromagnetic Induction

Induced Potential Difference  If the wire is moved perpendicular to the magnetic field and length of wire, a potential difference will be induced through the length of wire creating a current.  If the wire is moved parallel to the magnetic field, no potential difference will be induced.

Practice Problem 3  The diagram below represents a wire conductor, RS positioned perpendicular to a uniform magnetic field directed into the page. Which direction could the wire be moved to produce a maximum potential difference in the wire? X X X X X X R S Note: Magnetic field is directed into the page.

Generators  Potential difference can be increased by increased that rate at which the wire moves across magnetic field lines (moving faster or more magnetic field strength).  A generator produces electricity by turning mechanical energy (from a turbine) into electrical energy.

Electromagnets  Electric current going through a wire will create a magnetic field around that wire. If the wire is coiled around a piece of iron, that iron will become a very strong magnet as long as current flows.