1. Or Pimpin’ for Electricity
Magnetism
Or Pimpin’ for Electricity
Standards
5f Magnetic materials and electric currents (moving electric charges) are sources of magnetic fields and experience forces due to magnetic fields of other sources.
5g How to determine the direction of a magnetic field produced by a current flowing in a straight wire or in a coil.

2. Where do we observe magnetism?
Permanent magnets, around a current carrying wire and inside a looped wire
All of these involve accelerating electric charges.
Magnetism in general
Force between poles. Like poles repel, opposites attract
Produces fields that follow inverse square law with distance
Field direction North to South by convention
No magnetic monopoles
Magnetic force aligns magnetic particles
Magnetic fields made of loops
Question: Where do we observe the magnetic force? What causes a magnetic force? How is the magnetic force similar to the electric force? How does it differ?
Activity:
Demo: Show three types of magnetism seen yesterday with Levitron, wire through paper and loops around nail.
Remind students that saw three cases of magnetism yesterday: permanent magnets, magnetic field around a wire, magnetic field inside a coil. Discuss how all three involve the acceleration of electric charge and that this is the cause of all magnetism.
Make chart comparing electric and magnetic forces including what type of objects the particles are on, inverse square law, likes repel/opposites attract, both stronger than gravity.
Point out differences in magnetic and electric force including fact that there are no magnetic monopoles and this has the consequence of magnetic fields being loopy and magnetic force being an alignment force.
Show Phy Sci Video Chapter 42 on Magnets in space and ask students to explain what happened when magnets combined.

3. Permanent Magnets
Fe, Co, Ni, Nd have unpaired electrons in outer D orbitals with the same spin and can become magnets
Domain theory and Magnetic vs. non-magnetic iron
Dropping or heating magnet reduces strength
Cutting magnet in half results in two magnets both with a N and S pole.
Questions: Are all metals magnetic? Which are and what do they have in common? Draw a picture showing the difference between magnetic and non-magnetic iron. Explain why cutting a magnet in half results in two magnets? Explain why heating or dropping a magnet reduces its magnetism?
Activities:
Show Phy Sci Video 43 and 44 on cutting magnet in half and constructing a compus.
Remind students that saw yesterday that not all metals are magnetic. Iron, nickel, cobalt and neodymium are magnetic and are found in the metalloid part of the periodic table. This means the D or F shell is the outer shell. A closer look shows that all of these contain unpaired electrons in the orbitals of their outer shell. Currently it is felt that the alignment of the spins of these electrons is why these metals can be magnetized.
Draw magnetized and unmagnetized iron and explain how domain theory accounts for the difference.
Discuss how domain theory explains why cutting a magnet in half results in two magnets and why hitting or heating a magnet decreases its magnetism. Demo: Split magnet

4. Magnetic field around a current carrying wire
Field in shape of concentric loops
Field weakens as inverse square of distance from wire, direct relationship w/ current
RHR #2: Thumb in direction of current, fingers curl in direction of magnetic field
Question: Draw a wire and the magnetic field around it. How does this field vary with distance? How about with the current? State the second right hand rule. Will two wires with currents in the same direction attract or repel?
Activities:
Show Hewitt Video Oerstead’s discovery.
Show transparency and point out weakening of force with distance squared and increasing w/ current.
Point out that would like to find direction of field around wire.
Draw two wires with current going in and out of the board. Put compass needles around them. Discuss second right hand rule, demo with one of wires, have students do other wire
Do parallel wire problems
Demo: Current Balance

5. Looped Wire
More magnetization because have both linear and centripetal acceleration of charge
Magnetization is greatest inside of wire because of concentration of field lines in same direction
RHR #1 fingers curl in direction of conventional current, thumb points to north pole
RHR #1 also applies to single charges that spin or circle.
Question: What does looping a current carrying wire do to the magnetic field it produces? State right hand rule #1. Where does it apply?
Activities:
Show transparency of magnetic field around coil. Use 2nd RHR to show bunching of magnetic field in same direction. Ask what more coils would mean?
Introduce 1st right hand rule as method of more easily finding direction of magnetic field. Point out that rule shows where N pole is located and student must still find S pole and that direction of field is from N to S. Practice rule with currents in flat looped wires.
Point out that spinning as well as circling charges will produce magnetic field and go through magnetic fields around spinning protons and electrons using 1st RHR.

6. The Earth’s Magnetic Field
Shape of field is like a bar magnet
Believed to be caused by circulating charged ions in mantle and outer core
Field changes direction and strength over time
Field deflects charged particles from sun making life possible
Question: What is believed to be the cause of the Earth’s magnetic field? What is the shape of this field? How does it change over time? What does the field do to make life possible on Earth?
Activities:
Show slide picture of Earth’s magnetic field. Comment on how the north geographic pole is a south magnetic pole.
Discuss how circulation of charged particles in the mantle, outer core or both is believed to cause the magnetic field.
Discuss pole reversals and how the sea floor gave us a record of these changes.
Discuss deflecting of charges from sun and how this is essential to life. Show picture of real magnetic field.
Discuss future of field including reduction to nearly zero in next 200 or so years and flipping after that.