Chapter 36:Magnetism Conceptual Physics Bloom High School Mr. Barry Latham, M.A.Ed
36.1 Magnetic Poles • Magnets can attract and repel • Like repels, unlike attracts • Forces depend on distance • Inverse square rule! • Magnetic North- on a magnets, one end seeks the strongest north pole in the region • Magnetic South- on a magnets, the other end seeks the strongest south pole in the region • Always exists in pairs of N-S, even if you break the magnet in half!
36.2 Magnetic Fields • Lab 93! • PhET “Magnet & Compass 2.05”
36.3 The Nature of a Magnetic Field • Magnetic field caused by moving charges • In a magnet, the electrons are always moving • When they spin on their axis all in the same direction, they produce a magnetic field! • When they spin randomly, they don’t produce any field The Earth gets its magnetic field from spinning too!
36.4 Magnetic Domains • Magnetic domains- areas of a material that are either aligned or unaligned to each other • There is a degree of alignment • Non- not magnetic • Partial- weak magnet • Full- strong magnet
Creating Magnetic Domains • By putting a strong magnet near a non-magnet, it can cause the domains to align!
36.5 Electric Current & Magnetic Fields • Moving charges produce a magnetic field • Section 36.3 • When a current travels through a wire, a magnetic field is induced • Stronger current or more wires together • Stronger magnetic field • PhET “Magnets & Electromagnets 2.05”
36.6 Magnetic Forces on Moving Charged Particles • A static charge will not interact with a magnetic field • A moving charge will be deflected by a magnetic field, though! • Force is greatest when moving perpendicular to the field lines • Force is least when moving parallel • Magnetic field of Earth deflects most charged particles from the Sun and outer space • Aurora borealis is only seen near the poles, not the equator
36.7 Magnetic Forces on Current-Carrying Wires • Just as a single charge will be deflected by a magnetic field, a wire carrying a current will be deflected • The direction of the current will dictate the direction of deflection
36.8 Meters to Motors • Galvanometer • Just as a compass aligns to a magnetic field, a dial can be made to do the same thing • Ammeter • Galvanometer that measures current instead of magnetic field strength • Voltmeter • Galvanometer that measures voltage instead of magnetic field
Motors • If we have an alternating current, then the magnets will spin back and forth, trying to keep up with the frequency of voltage change • http://www.youtube.com/watch?v=it_Z7NdKgmY