MAGNETISM Normally denoted by B Magnetic forces affect moving charged particles* Forces are perpendicular to both magnetic field and direction of motion *Or objects made of charged particles Magnetic Field B velocity v charge q Force F

Magnetic units Magnetic field units: Ns/Cm Called a Tesla (T) A Tesla is a big magnetic field MRI magnet -> 1-4 Tesla

Electric Field Lines Graphical Illustration of Electrical Fields Lines start on positive charges and end on negative Number of lines from/to a charge is proportional to that charge Density of lines tells strength of field. + - + -

Magnetic Field Lines Graphical Illustration of Magnetic Fields Lines start on north pole and end on south pole Opposite poles attract, like poles reply Density of lines tells strength of field. Key differences between magnetic fields and electric fields: All magnets have a north and south pole! No such thing as an isolated north or south pole. (have magnetic dipoles, not monopoles) Different force laws!

Vector Product Vector product -> two vectors make a vector Geometric C has magnitude ABsinq. Direction perpendicular to the plane containing A and B. Algebraic

The right hand rule Force F velocity v Magnetic Field B

Magnetic Force Can only affect moving particles! Force depends on charge just like electric fields Force is maximum when the velocity and field are perpendicular, and zero when they are parallel When the velocity and field are neither perpendicular nor parallel, the force still exists!

3-d directions of vectors into the plane The two vectors shown represent the velocity and the magnetic field. For a negatively charged particle, which way will the particle accelerate? A) C) B) D) velocity v Magnetic Field B out of the plane