Static Electricity 1
1020 C1020 CStatic ElectricityStatic Electricity
Chapter 10 part 1Chapter 10 part 1
Static Electricity 2
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
Static Electricity 3
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
Static Electricity 4
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?
Static Electricity 5
Question 1Question 1
Why do some clothes cling while Why do some clothes cling while others repel?others repel?
Static Electricity 6
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)
Static Electricity 7
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
Static Electricity 8
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.
Static Electricity 9
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.
Static Electricity 10
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
Static Electricity 11
Question 2Question 2
Why do clingy clothes stick to Why do clingy clothes stick to uncharged walls?uncharged walls?
Static Electricity 12
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
Static Electricity 13
Question 3Question 3
Why do clingy clothes crackle as Why do clingy clothes crackle as they separate?they separate?
Static Electricity 14
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
Static Electricity 15
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.
Static Electricity 16
Question 4Question 4
Why do some things lose their Why do some things lose their charge quickly?charge quickly?
Static Electricity 17
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.
Static Electricity 18
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.