1. Charging by Induction

2. Charging by Induction: Temporarily
When a charged object is brought close to, but not touching, a neutral object, the electrons in the neutral object move either away from or toward the charged object.
When electrons move within an object because of a nearby charged object, it is called induced charge separation.
induced charge separation
charging by induction

3. Charging by Induction: Temporarily

4. Charging by Induction: Temporarily
Once the charged object is moved away, the electrons in the neutral object return to their original positions.

5. Charging by Induction: Permanently
You can permanently charge an object using induction. To do this, you need to ground the neutral object.

6. Charging by Induction: Permanently_ _ _ _
A negatively charged object is placed near a neutral object, causing the electrons to move.

7. Charging by Induction: Permanently_ _ _ _
The neutral object is grounded, allowing the repelled electrons in the neutral object to escape to the ground. The neutral object loses electrons.

8. Charging by Induction: Permanently_ _ _ _
The ground is removed, leaving the ball with a positive charge.

9. Charging by Induction: Permanently
If electrons move from the neutral object through the wire to the ground (object loses electrons), the object becomes positively charged.
If electrons move from the ground through the wire toward the object (object gains electrons), the object becomes negatively charged.

10. Charging by Induction: Permanently
Animation of Permanent Induction

11. Applications of Static Electricity
Science principles involved
How the application works
Electrostatic speakers
charging by induction, law of electric charges
In an electrostatic speaker, an audio transformer induces opposite electrical charges on two outer plates (stators) and then (b) reverses them.

12. Note: Charging by Induction
This method of charging objects involves no contact between a charged object and a neutral object, and grounding is used.

13. Note: Charging by Induction1.
Negative
Neutral

14. Note: Charging by Induction1.
Negative e-
Neutral

15. Note: Charging by Induction1.
A negatively charged rod is placed near a neutral object. The excess electrons in the rod repel the _____________ in the object making them move as far away from the rod as possible. This shifting of electrons makes one side of the object __________________ and the other side _________________ (however, the object is still neutral). This is called _____________________________.
electrons
positive
negative
induced charge separation

16. Note: Charging by Induction2. e-
Negative
Ground

17. Note: Charging by Induction2.
If the neutral object is grounded, the repelled electrons move from the ____________ to the ___________ (the object _________ electrons).
object
ground
loses

18. Note: Charging by Induction3.
Negative
Positive

19. Note: Charging by Induction3.
When the ground is removed, the object is left with a _____________ charge (because it _________ electrons to the ground).
positive
lost

20. Note: Charging by Induction
*** When objects are permanently charged by induction, the induced charge is always ______________ that of the charged object.
opposite

21. Charging by Induction Questions 1. Temporary Induction
A. A neutral metal-leaf electroscope.
B. A negatively charged object is placed near (not touching) the metal ball of a neutral metal- leaf electroscope.
C. The charged object has been removed.

22. Charging by Induction Questions 1. Temporary Induction
A. A neutral metal-leaf electroscope.
B. A negatively charged object is placed near (not touching) the metal ball of a neutral metal- leaf electroscope.
C. The charged object has been removed. e-

23. Charging by Induction Questions 1. Temporary Induction
A. A neutral metal-leaf electroscope.
B. A negatively charged object is placed near (not touching) the metal ball of a neutral metal- leaf electroscope.
C. The charged object has been removed. e-

24. Charging by Induction Questions 1. Temporary Induction
A. A neutral metal-leaf electroscope.
B. A negatively charged object is placed near (not touching) the metal ball of a neutral metal- leaf electroscope.
C. The charged object has been removed. e-

25. Charging by Induction Questions 2. Permanent Induction
A. A positively charged object is placed near (not touching) a neutral electroscope.
B. The electroscope is then grounded.
C. The ground is removed. Then the charged object is removed.

26. Charging by Induction Questions 2. Permanent Induction
A. A positively charged object is placed near (not touching) a neutral electroscope.
B. The electroscope is then grounded.
C. The ground is removed. Then the charged object is removed. e- e-

27. Homework
p. 489 # 2, 3, 4, 6