Principles of Physics Magnetism and Electricity

3 Dimensional Directions Right Left Up Down Into Out of page page xxxxx

Current and Magnets In the presence of moving charge (current) a compass will rotate so, current carrying wires exert magnetic force When the wire is wrapped in a loop poles form on each side of it For a stronger B-field more loops (solenoid) loops wrapped around a magnetic core (electromagnet)

More on how materials become magnetized… Electrons move in tiny circular paths generating their own magnetic fields Electrons are grouped in areas called domains B-fields of electrons in each domain are lined up Together they act as one stronger B-field The magnetic effect is even stronger when domains line up.

More on how materials become magnetized… Materials that can become magnetized have domains that can shift in order to line up. High permeability = domains shift easily Low permeability = domains hard to shift

Force on a Current Carrying Wire Current carrying wires placed near a magnet can experience force force causes wire to move current must flow perpendicular to the B-field * single charges can also experience a force in a B field

Force on a Current Carrying Wire F = I l B F = force (N) I = electron flow (A) l = length of wire (m) B = Magnetic Field strength (Tesla = T = N/Am)

Example Problem The current flowing in a 2.0 m wire is 100 A. The wire is placed in a magnetic field of T such that it is oriented perpendicular to the field. Calculate the force experienced by the wire. F = I l B F = 100 A(2.0 m)(0.003 T ) F = 0.6 N

Left Hand Rule Thumb = direction of e - flow Fingers = direction of B-field Palm = force Current (e - flow) Force Magnetic Field

Examples NS e-e- Force: into page

Examples NS x Force: top of page

Examples x N S Force: right

Examples N S Force: left