1. Electrostatics: Electricity at Rest
Chapter 32
Electrostatics:
Electricity at Rest
Electricity at rest – not moving yet – that is later- harder

2. Facts About the Atom Positively Charged particles (protons)
located inside the nucleus
has a fixed position

3. Facts About the Atom Negatively Charged particles (electrons)
located in the electron cloud
negligible mass; smaller than the proton
mobile
lose/gain electrons
electron

4. Facts About the Atom Neutral Atom Neutrons no attraction/repulsion
located in the nucleus
Neutral Atom
# protons = # electrons
zero net charge

5. Electrical Charges
Fundamental Rule:
Like charges repel
Opposite Charges Attract

6. Conservation of Charge
Total amt. Of charge remains the same but may be rearranged.
Fur: neutral Rod: neutral
Neutral Fur gives 2 million electrons to rubber rod
Fur: +2 million charge Rod: -2 million charge
Like mass conservation, matter conservation, energy, momentum

7. Conductors vs. Insulators
Charged Particles that can move
Metals
electron sea
Tightly bound electrons
Rubber
Glass
ALL about the electrons!!

8. Forces Newton’s Law of Universal Gravitation F = G m1m2 d2 Attractive
Depends on mass
G = small magnitude = weak force
Remember from Chapter 12

9. Forces Coulomb’s Law F = k q1q2 d2 Attractive or Repulsive
Depends on Charge
k = large magnitude = strong force

10. Coulomb’s Law F = k q1q2 d2 k = 9.0 x 109 N•m2/C2
Unit of Charge - Coulomb (C)
Discuss attraction vs. repulsion with sign of charges and sign of force

11. Coulomb’s Law
Sirap rubs two latex balloons against her hair, causing each balloon to become charged negatively with 2.0 x 10-6 C. She holds them a distance of 0.70 m apart. What is the electric force between the two balloons?

12. Coulomb’s Law
When sugar is poured from the box into the sugar bowl, the rubbing of sugar grains create a static electric charge. If two sugar grains each acquire a charge of 3.0 x C at a separation of m, with what force will they repel?

13. Coulomb’s Law
Two balloons acquire a charge of 2.0 x 10-7 C each. How large is the electric force between them when they are separated by a distance of 0.50 m?

14. Coulomb’s Law
A raindrop acquires a negative charge of 3.0 x C as it falls. What is the force of attraction when the raindrop is 6.0 cm from the end of a car antenna that holds a charge of 2.0 x 10-6 C?

15. Coulomb’s Law
In a grain elevator, pieces of grain become electrically charged while falling through the elevator. If one piece of grain is charged with 5.0 x C while another holds a charge 2.0 x C. What is the force between them if they are separated by m?

16. Induction Charged object is brought near to neutral object…
Neutral object polarizes
Electricity attraction!
Induce ‘cause to happen now’ induced vomiting, inducing delivery of a baby
No charge actually switches items!

17. Lightning!! Clouds build up static electricity
Ground is inductively charged
Discharge!!!
Lightning rods – slowly drain charge
Use Ellen’s Video – start at 12 minutes to discuss how clouds get charged
2 reasons for lightning rods