1. Charging By Contact and by Induction

2. Detecting Charges  An electroscope is a simple device that is used to detect the presence of electric charges.  Pith ball and metal leaf electroscopes are most common.

3. Pith Ball  small, light ball on a cotton thread.  If a charged object comes close, the neutral pith ball will be attracted to the charged object.

4. Metal Leaf Electroscope  a sphere connected to a rod, which has metal leaves at the end of it.  All made of metal to allow free flow of electrons

5. Charge by Contact  Happens when contact is made between a neutral object and a charged object.  The object that becomes charged through contact will always have the same charge as the initial object that touched it.

6. +-+- - +---++---+ +---++---+ +---++---+ +- Before contactduring contactafter contact Neg. rod, electrons transfer-both are neg. Neutral ball red to ballrepel each other

7. Charging by Induction  When a charged object is near a neutral object, the electric field of the charged object has an effect on the neutral object.  The charged object induces electrons in the neutral object to move.  Happens without contact.

8. Questions:  P. 415 # 1, 2.  P.417 # 1, 3, 6, 7, 8.  See p. 419. Draw a diagram on how lightning works.