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Magnetism and Electricity. Principles of Physics. 3 Dimensional Directions. Right Left Up Down Into Out of page page. xxxxx xxxxx xxxxx. • • • • • • • • • • • • • • • . Current and Magnets. In the presence of moving charge (current) a compass will rotate
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Magnetism and Electricity Principles of Physics
3 Dimensional Directions Right Left Up Down Into Out ofpage page xxxxx xxxxx 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 = IlB 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 0.003 T such that it is oriented perpendicular to the field. Calculate the force experienced by the wire. F = IlB 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 Magnetic Field Current (e- flow) Force
Examples e- N S Force: into page
Examples N S x Force: top of page
N x S Examples Force: right
N • S Examples Force: left