1. 10.2 Charging By Contact and By Induction (Pages 411-416) Homework: Page 417 # 2-5, 7, 8 Key Concepts: (Page 417)

2. An electroscope is a device that is used to detect the presence of an electric charge. There are three laws of electric charges: Like charges repel; Opposite (unlike) charges attract; Neutral objects and charged objects are attracted to each other. Copy down Figure 10.12 (p. 413)

3. An object that is charged by contact has the same type of charge as the charging object. An electric force between two objects is transmitted by an electric field. An induced charge separation is the movement of electrons in a substance, caused by the electric field of a nearby charged object. Watch This!

4. What is an electroscope? An electroscope is a device that detects the presence of an electric charge

5. 2. Compare & Contrast – Charging by contact Takes place when contact is made between a neutral object and an object that is charged An object that becomes charged by contact always gets the same type of charge that is on the object that charges it –Ex. Ball (negatively charged) comes in contact with rod (neutral, no charge)  rod becomes negatively charged

6. Charging by friction Two different materials One material has a stronger attraction to electrons (which are negatively charged) than another material Therefore, electrons are pulled off the material that has the weaker attraction for them Both materials become charged due to an excess or shortage of electrons

7. Charging by induction The movement of electrons in a substance, caused by the electric field of a nearby charged object (positive or negative) without direct contact between the substance & the object The electric field of the charged object produces a force on the neutral object Example: –A Rod (negative) comes in contact with a ball (neutral) and the electrons in the ball move away from the rod (because similar charges repel) –This creates a positive side to the ball which becomes attracted to the negative rod & causes it to move towards the rod