static electricity 1 1020 c static electricity chapter 10 part 1

Static Electricity 1

1020 C1020 CStatic ElectricityStatic Electricity

Chapter 10 part 1Chapter 10 part 1


Introductory QuestionIntroductory Question

A woman rubs her feet on the carpet A woman rubs her feet on the carpet and gives a shock to her identical and gives a shock to her identical twin. If the twin also rubs her feet on twin. If the twin also rubs her feet on the carpet before being touched, the the carpet before being touched, the shock will beshock will be

A.A. largerlarger

B.B. smallersmaller

C.C. the same sizethe same size


Observations aboutObservations aboutStatic ElectricityStatic Electricity

Static electricity builds up on non-Static electricity builds up on non-metallic thingsmetallic things

Objects with static charge may cling Objects with static charge may cling or repelor repel

Static electricity can lead to shocksStatic electricity can lead to shocks Static electricity can make your hair Static electricity can make your hair

stand upstand up


4 Questions about4 Questions aboutStatic ElectricityStatic Electricity

Why do some clothes cling while Why do some clothes cling while others repel?others repel?

Why do sticky clothes stick to Why do sticky clothes stick to uncharged walls?uncharged walls?

Why do clingy clothes crackle as Why do clingy clothes crackle as they separate?they separate?

Why do some things lose their Why do some things lose their charge quickly?charge quickly?


Question 1Question 1

Why do some clothes cling while Why do some clothes cling while others repel?others repel?


Electric Charge Electric Charge (Part 1)(Part 1)

Charges appear in two types: positive & Charges appear in two types: positive & negativenegative Like charges repelLike charges repel Opposite charges attractOpposite charges attract

Two charges push (or pull) on one Two charges push (or pull) on one anotheranother with forces that are exactly equal in with forces that are exactly equal in

magnitudemagnitude but exactly opposite in direction.but exactly opposite in direction.

The forces increase as the separation The forces increase as the separation decreasesdecreases

1 22

Coulomb constant charge chargeforce =

(distance between charges)


Electric Charge Electric Charge (Part 2)(Part 2)

Electric chargeElectric 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


Net ChargeNet Charge

An object’s net chargeAn object’s net charge is the sum of its individual chargesis 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 hasA neutral object has zero net chargezero net charge and contains as many + charges as – and contains as many + charges as –

charges.charges.


Charge TransfersCharge Transfers

Contact can transfer charge between objectsContact can transfer charge between objects The object with the stronger affinity for electronsThe object with the stronger affinity for electrons becomes negatively charged upon contactbecomes negatively charged upon contact will the other object becomes positively charged.will the other object becomes positively charged. These oppositely charge objects attract one These oppositely charge objects attract one

another.another. Rubbing the objects together ensuresRubbing the objects together ensures

excellent contact between their surfacesexcellent contact between their surfaces and consequently substantial charge transfer.and consequently substantial charge transfer.


Introductory Question Introductory Question (revisited)(revisited)

A woman rubs her feet on the carpet A woman rubs her feet on the carpet and gives a shock to her identical and gives a shock to her identical twin. If the twin also rubs her feet on twin. If the twin also rubs her feet on the carpet before being touched, the the carpet before being touched, the shock will beshock will be

A.A. largerlarger

B.B. smallersmaller

C.C. the same sizethe same size



Why do clingy clothes stick to Why do clingy clothes stick to uncharged walls?uncharged walls?


Electric PolarizationElectric Polarization

A neutral wall contains countless chargesA 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 wallThe charged sock clings to the polarized wall



Why do clingy clothes crackle as Why do clingy clothes crackle as they separate?they separate?


VoltageVoltage

Charge has electrostatic potential Charge has electrostatic potential energy (EPE)energy (EPE)

Voltage measures the EPE per unit of Voltage measures the EPE per unit of chargecharge Raising the voltage of positive charge takes Raising the voltage of positive charge takes

workwork Lowering the voltage of negative charge Lowering the voltage of negative charge

takes worktakes work Voltage is measured in joules/coulomb Voltage is measured in joules/coulomb

or voltsor volts


Separating Opposite Separating Opposite ChargesCharges

Separating opposite charges takes work,Separating opposite charges takes work, so the positive charges undergo a rise in voltageso the positive charges undergo a rise in voltage and the negative charges undergo a drop in and the negative charges undergo a drop in

voltage.voltage. Positive charge at high voltage can release Positive charge at high voltage can release

EPEEPE by moving to lower voltageby moving to lower voltage and it often does this by way of a discharge or and it often does this by way of a discharge or

spark!spark! Negative charge behaves oppositely,Negative charge behaves oppositely,

releasing EPE by moving to higher voltage.releasing EPE by moving to higher voltage.



Why do some things lose their Why do some things lose their charge quickly?charge quickly?


Conductors and Conductors and InsulatorsInsulators

All objects contain positive and negative All objects contain positive and negative chargescharges but most of those charges are immobile.but most of those charges are immobile.

Insulators have no mobile electric Insulators have no mobile electric chargescharges

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.


Summary aboutSummary aboutStatic ElectricityStatic Electricity

Even neutral objects contain countless Even neutral objects contain countless chargescharges

Charge can be transferred during contactCharge can be transferred during contact Clothes often develop net charges during Clothes often develop net charges during

dryingdrying Oppositely charged clothes cling to one Oppositely charged clothes cling to one

anotheranother and spark as separation affects their and spark as separation affects their

voltages.voltages. Conductivity tends to let objects neutralize.Conductivity tends to let objects neutralize.

static electricity 1 1020 c static electricity chapter 10 part 1

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