110 likes | 246 Views
Exam 3 Review. Magnetic Fields Faraday’s Law. Magnetic field. Field lines come out of the NORTH end of a bar magnet. Field produced by a wire Field produced by a loop or a coil Field produced by a solenoid. Magnetic Forces on Moving Charges.
E N D
Exam 3 Review Magnetic Fields Faraday’s Law
Magnetic field • Field lines come out of the NORTH end of a bar magnet. • Field produced by a wire • Field produced by a loop or a coil • Field produced by a solenoid
Magnetic Forces on Moving Charges • Charge q, moving with velocity v in magnetic field B, v makes and angle αwrt B : • Mass spectrometer: v ┴ B, circular path of radius
Magnetic Force on Currents • Current carrying wire perpendicular to B • FWIRE = ILB • Force between parallel wires • Currents in same direction attract, opposite repel
Magnetic torque on dipole • Θ is the angle between the magnetic field B and the perpendicular to the plane of the loop. • Torque on loop is • Loop lies in a plane • No MRI questions
Motional EMF • Straight wire of length L moving perpendicularly to a uniform magnetic field B • EMF = v L B
Magnetic Flux • Θ is the angle between perpendicular to loop and the magnetic field
Lenz’s Law • Current induced in a loop by a changing magnetic flux creates a magnetic field which opposes the change in flux.
Faraday’s Law • Changing magnetic flux induces an EMF: • Lenz’s law gives direction • Faraday’s law gives magnitude:
Flux changes • Change magnetic field • For a coil: