1. Your assignment for tonight: Read Pages 541- 553.
Answer questions:
Page 545 Answer Problems 1-8
Page 552 Complete problems
Page 553 Answer problems 14-21

2. Quick Question:
What is an electroscope and what can we learn from using one?
What is an elementary charge?
If you comb your hair on a dry day, the comb can become positively charged. Can you hair remain neutral? Explain.
Using a charged rod and an electroscope, how can you find whether or not an object is a conductor?

3. Quick Question:
What is an electroscope and what can we learn from using one?
A simple piece of equipment
used to determine electric
charge, conductors, and
insulators.

4. Quick Question:
What is an elementary charge?
An elementary charge is the charge carried by a single electron (or proton).

5. Quick Question:
If you comb your hair on a dry day, the comb can become positively charged. Can you hair remain neutral? Explain.
No. By the law of conservation of charge, your hair must become negatively charged. The electrons that left the comb are now on your hair.

6. and the object is a conductor.
Quick Question:
Using a charged rod and an electroscope, how can you find whether or not an object is a conductor?
Use a known insulator to hold one end of the object against the electroscope. Touch the other end with the charged rod. If “leaves” move, it indicates a charge
and the object is a conductor.
Hyperlink picture

7. Today’s Objective: I can use electroscopes to determine charges.

8. If the object has a positive charge, it will pull electrons up to the top terminal. This will cause the leaves of the electroscope to be more positively charged, causing them to move further apart.

9. If the object has a negative charge, it will repel electrons from the top terminal. This pushes electrons down to the leaves, causing them to be less positively charged, causing them to drop towards each other.

10. If the object has a much larger negative charge than the positive charge on the electroscope, as you move it closer the leaves will drop to touch, then begin to rise again as so many electrons will be repelled from the top plate that there are now more negative charges than positive in the leaves and they will repel again

11. A glass rod rubbed with silk will make a positive charge.

12. Today’s Objective: I can calculate the potential difference from the work required to move a charge.