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1020 C Static Electricity

1020 C Static Electricity. Chapter 10 part 1. 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 larger smaller the same size.

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1020 C Static Electricity

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  1. 1020 CStatic Electricity Chapter 10 part 1

  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 • larger • smaller • the same size

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

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

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

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

  7. Electric Charge (Part 2) • Electric charge • is a conserved quantity, • is measured in coulombs, • 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. Net Charge • An object’s net charge • is the sum of its individual charges • and tends to be zero or nearly zero. • A neutral object has • zero net charge • and contains as many + charges as – charges.

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

  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 • larger • smaller • the same size

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

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

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

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

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

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

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

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

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