1. Static Electricity 1 1020 C Static Electricity Chapter 10 part 1

2. Static Electricity 2 Introductory Question A woman rubs her feet on the carpet and gives a shock to her identical twin. If the twin also rubs her feet on the carpet before being touched, the shock will be A woman rubs her feet on the carpet and gives a shock to her identical twin. If the twin also rubs her feet on the carpet before being touched, the shock will be A. larger B. smaller C. the same size

3. Static Electricity 3 Observations about Static Electricity Static electricity builds up on non-metallic things Static electricity builds up on non-metallic things Objects with static charge may cling or repel Objects with static charge may cling or repel Static electricity can lead to shocks Static electricity can lead to shocks Static electricity can make your hair stand up Static electricity can make your hair stand up

4. Static Electricity 4 4 Questions about Static Electricity Why do some clothes cling while others repel? Why do some clothes cling while others repel? Why do sticky clothes stick to uncharged walls? Why do sticky clothes stick to uncharged walls? Why do clingy clothes crackle as they separate? Why do clingy clothes crackle as they separate? Why do some things lose their charge quickly? Why do some things lose their charge quickly?

5. Static Electricity 5 Question 1 Why do some clothes cling while others repel? Why do some clothes cling while others repel?

6. Static Electricity 6 Electric Charge (Part 1) Charges appear in two types: positive & negative Charges appear in two types: positive & negative Like charges repel Like charges repel Opposite charges attract Opposite charges attract Two charges push (or pull) on one another Two charges push (or pull) on one another with forces that are exactly equal in magnitude with forces that are exactly equal in magnitude but exactly opposite in direction. but exactly opposite in direction. The forces increase as the separation decreases The forces increase as the separation decreases

7. Static Electricity 7 Electric Charge (Part 2) Electric charge Electric charge is a conserved quantity, is a conserved quantity, is measured in coulombs, is measured in coulombs, is is quantized in multiples of the fundamental charge. One fundamental charge is 1.6  10 -19 coulombs Charge is an intrinsic property of matter Electrons are negatively charged Protons are positively charged Each has one fundamental charge

8. Static Electricity 8 Net Charge An object’s net charge An object’s net charge is the sum of its individual charges is the sum of its individual charges and tends to be zero or nearly zero. and tends to be zero or nearly zero. A neutral object has A neutral object has zero net charge zero net charge and contains as many + charges as – charges. and contains as many + charges as – charges.

9. Static Electricity 9 Charge Transfers Contact can transfer charge between objects Contact can transfer charge between objects The object with the stronger affinity for electrons The object with the stronger affinity for electrons becomes negatively charged upon contact becomes negatively charged upon contact will the other object becomes positively charged. will the other object becomes positively charged. These oppositely charge objects attract one another. These oppositely charge objects attract one another. Rubbing the objects together ensures Rubbing the objects together ensures excellent contact between their surfaces excellent contact between their surfaces and consequently substantial charge transfer. and consequently substantial charge transfer.

10. Static Electricity 10 Introductory Question (revisited) A woman rubs her feet on the carpet and gives a shock to her identical twin. If the twin also rubs her feet on the carpet before being touched, the shock will be A woman rubs her feet on the carpet and gives a shock to her identical twin. If the twin also rubs her feet on the carpet before being touched, the shock will be A. larger B. smaller C. the same size

11. Static Electricity 11 Question 2 Why do clingy clothes stick to uncharged walls? Why do clingy clothes stick to uncharged walls?

12. Static Electricity 12 Electric Polarization A neutral wall contains countless charges A neutral wall contains countless charges that respond to any nearby charged object. that respond to any nearby charged object. When a negatively charged sock nears a wall, When a negatively charged sock nears a wall, the wall’s positive charges shift toward the sock, the wall’s positive charges shift toward the sock, the wall’s negative charges shift away from it, the wall’s negative charges shift away from it, and the wall becomes electrically polarized. and the wall becomes electrically polarized. The charged sock clings to the polarized wall The charged sock clings to the polarized wall

13. Static Electricity 13 Question 3 Why do clingy clothes crackle as they separate? Why do clingy clothes crackle as they separate?

14. Static Electricity 14 Voltage Charge has electrostatic potential energy (EPE) Charge has electrostatic potential energy (EPE) Voltage measures the EPE per unit of charge Voltage measures the EPE per unit of charge Raising the voltage of positive charge takes work Raising the voltage of positive charge takes work Lowering the voltage of negative charge takes work Lowering the voltage of negative charge takes work Voltage is measured in joules/coulomb or volts Voltage is measured in joules/coulomb or volts

15. Static Electricity 15 Separating Opposite Charges Separating opposite charges takes work, Separating opposite charges takes work, so the positive charges undergo a rise in voltage so the positive charges undergo a rise in voltage and the negative charges undergo a drop in voltage. and the negative charges undergo a drop in voltage. Positive charge at high voltage can release EPE Positive charge at high voltage can release EPE by moving to lower voltage by moving to lower voltage and it often does this by way of a discharge or spark! and it often does this by way of a discharge or spark! Negative charge behaves oppositely, Negative charge behaves oppositely, releasing EPE by moving to higher voltage. releasing EPE by moving to higher voltage.

16. Static Electricity 16 Question 4 Why do some things lose their charge quickly? Why do some things lose their charge quickly?

17. Static Electricity 17 Conductors and Insulators All objects contain positive and negative charges All objects contain positive and negative charges but most of those charges are immobile. but most of those charges are immobile. Insulators have no mobile electric charges Insulators have no mobile electric charges Conductors have mobile electric charges, Conductors have mobile electric charges, which are usually electrons (e.g., metals) which are usually electrons (e.g., metals) but are occasionally ions (e.g., salt water). but are occasionally ions (e.g., salt water). Conductors can lose net charges easily. Conductors can lose net charges easily.

18. Static Electricity 18 Summary about Static Electricity Even neutral objects contain countless charges Even neutral objects contain countless charges Charge can be transferred during contact Charge can be transferred during contact Clothes often develop net charges during drying Clothes often develop net charges during drying Oppositely charged clothes cling to one another Oppositely charged clothes cling to one another and spark as separation affects their voltages. and spark as separation affects their voltages. Conductivity tends to let objects neutralize. Conductivity tends to let objects neutralize.