AP Physics B Objectives

Links:

College Board Topic III:
Electricity and Magnetism

Topics:

1. Electrostatics
   1. Charge, field, and potential
   2. Coulomb's law and field and potential of point charges
   3. Fields and potentials of planar charge distributions

Time Range:
3 or 4 weeks

Suggested Teaching Strategies:

• Have students in groups use electroscopes (e.g. pith ball, vane, leaf) and friction rods (e.g. plastic rod with silk, hard rubber rod with fur) to illustrate basic charge rules, charge separation, and conduction. Demonstrate Faraday cylinder to illustrate how charge remains on the exterior of a conductor with applications for electric shielding (e.g. cars in lightning storms, metal cages around computer chips).
• Have students examine induction with electrophori, and illustrate concept with old-style and dissectible Leyden jars.
• Use van de Graaff and Wimhurst generators to illustrate charge redistribution and related effects.
• Compare Coulomb's Law to Newton's Law of Universal Gravitation and have students practice vector math with simple geometrical charge distributions and resultant forces.
• Computer simulations can illustrate electric field lines of force - actual demonstrations with grass seed & mineral oil or fibrils on overhead are often unimpressive. Be sure to cover quantitative vector analysis of electric fields as well as basic voltage concepts.

Aligned Resources:

• Available student lab equipment includes: pith ball, leaf, and vane electroscopes; hard rubber and plastic friction rods (glass available but not recommended); silk, flannel, and fur friction pads; electrophori
• Demonstration equipment includes: Faraday cylinder, larger higher-quality instructor electrophorus, old-style and dissectible Leyden jars. Wimhurst generator can produce significant sparks when Leyden jars engaged; observe safety precautions. Three different van de Graaff generators available, with separate electrode sphere or wand, electric whirls, Volta's chamber, insulating stool, etc. Do NOT allow students with heart conditions to participate in such demonstrations. Portable Tesla coil also available in chemistry department.
• Videotape: Raging Planet - Lightning from Discovery Channel (or older NOVA special Lightning!)
• Videotape segment of 1,000,000 V Tesla Coil, Faraday Cage, and "Human Light Bulb" on one of Clint Sprott's Wonders of Physics demonstration tapes
• Simulations of electric fields on textbook CD-ROM's and Physics by Pictures software.
• Available demonstration equipment: Electric fields apparatus for overhead projector, with electrodes to connect to high-voltage power supply and fibrils to spread around electrodes.

Revision Date:
November 2001