Warm-Up April 30, 2013 In your notebooks, answer the following questions: If you scuff electrons from your hair onto a comb, are you (your hair) positively or negatively charged? What about the charge of the comb?

Charging by friction! Which objects are positively charged and which are negatively charged? Will they eventually lose their charge?

Electrostatics: review Get out your notebooks Electrostatics - electricity "at rest", aka "static electricity"; electricity in its "natural form", without being pushed through wires by batteries or generators. What is charge? How do things get a charge? Protons vs. Electrons; like repels like, opposites attract.

Electric force fields depending on charge. Do you observe forces of attraction or repulsion? Do these force fields resemble gravitational force fields? Why or why not?

Most objects have a neutral or balanced charge (ie, no charge) because their protons and electrons are more or less equal. Charged objects are unbalanced. Conservation of Charge: If an object "loses electrons", then it becomes positively charged and the "travelling" electrons negatively charge some other object. Coulomb's Law: used to calculate charge and the amount of force between charged objects; either repulsion or attraction; reminiscent of Newton's Law of Gravitation.

Three ways to charge an object: Insulators, conductors, and semiconductors - How do they help or hamper the flow of electrons? Three ways to charge an object: friction, simple contact, or induction Grounding

Today's Assignment: Complete the double-sheet handout and submit to the basket before you leave. Be sure you've completed and submitted yesterday's set of questions (handout). You should have enough time to complete the assignment. When done, quietly use the remaining class time wisely.