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Unit #7
Magnetism / Electromagnetism--Objectives
text: ch 20 sec 1-7; ch 21 sec 1-7;
1 answer the question, "What is a magnet?" and in so doing 1) distinguish between permanent magnets and magnetic
materials, 2) after noting that magnets have two opposite poles, distinguish magnetic poles / electric charge; recognize
electricity & magnetism are intimately connected and the ultimate source of any magnetic field is moving charge
2 describe the forces between two permanent magnets; recognize most materials don't shield magnetic forces; explain
why magnetic forces decrease rapidly with distance; describe the torque between two magnets
3 recognize similarities between electric / magnetic field representations, noting interpretation of magnetic field is
more complicated and that it can be mapped by orientation of test compass; sketch the magnetic field for a bar magnet
4 describe Earth's magnetic field by relating it to bar magnet; identify source of Earth's magnetism; identify / relate
tesla, gauss; connect with Earth's average field strength; describe how compass is used to find direction north
5 describe Oersted's experiment; realize electric currents produce magnetic fields; use the right hand rule to determine
the direction of the magnetic field produced by the current in a wire
6 calculate the magnitude of the magnetic force on a current carrying wire placed in a region of uniform magnetic
field; use the right hand rule to find the direction of this force; work related problems
7 calculate the magnitude of the magnetic force on a moving electric charge in a region of uniform magnetic field; use
the right hand rule to find the direction of this force; work related problems
8 calculate the magnitude of the magnetic field near a current carrying wire; work related problems
9 calculate the magnitude of the magnetic force between two parallel current carrying wires, and describe its direction;
work related problems; realize ampere and coulomb are practically defined using this experimental setup
10 realize that weak magnetic fields around wires can be strengthened by wrapping them to make coils; describe
magnetic field around coil of many loops; identify solenoid, electromagnet; realize magnetic field inside solenoid is
nearly uniform and its strength depends on current and number of turns per unit length; identify uses of solenoids
11 explain electromagnetic induction (induced emf) by describing a simple demo showing how current is induced;
describe experiments of Faraday and Oersted that resulted in basic principles of electromagnetism; identify them
12 determine the magnitude of the magnetic flux through a surface of known area, given the strength of the magnetic
field and the angle between the direction of the magnetic field and the surface
13 write a statement of Faraday's law in terms of changing magnetic flux; use Faraday's law to determine the
magnitude of the induced emf in a closed loop due to a change in the magnetic flux through the loop
14 use Faraday's law to find the magnitude of the induced emf in a conducting rod moving through a magnetic field
15 state Lenz' law and use Ohm's law and Lenz's law to determine the magnitude and direction of the induced current
16. explain the basic principle of the electric generator; determine the magnitude of the maximum value of the induced
emf in a loop which is rotating at a constant rate in a uniform magnetic field; realize that generators and motors
involve opposite energy conversions and that some motors can be used as generators