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

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

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

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

Electrical Charges Fundamental Rule: Like charges repel Opposite Charges Attract

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

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

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

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

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

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?

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 10-11 C at a separation of 0.00080 m, with what force will they repel?

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?

Coulomb’s Law A raindrop acquires a negative charge of 3.0 x 10-18 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?

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 10-16 C while another holds a charge 2.0 x 10-16 C. What is the force between them if they are separated by 0.050 m?

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!

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