conceptual physics notes on chapter 33 electric fields & potential

Conceptual PhysicsConceptual PhysicsNotes on Chapter 33Notes on Chapter 33

Electric Fields & Potential


““May the FORCE be with May the FORCE be with youyou””


All particles All particles have an have an electric fieldelectric field around them. around them.

A electric A electric field is a kind field is a kind of of auraaura that that extends extends outward outward through through spacespace. .


To show the To show the effects of the effects of the electric field, electric field, we use a we use a ““small test small test chargecharge” ” ((which is which is positivepositive) to ) to determine the determine the direction and direction and strength of strength of the field.the field.


Since the field has Since the field has magnitudemagnitude and and directiondirection it is it is

a vector and can a vector and can be represented be represented with with vectorsvectors. .

These vectors are called These vectors are called Field linesField lines or or Lines of forceLines of force

(See fig. 33.3 pg. 519)(See fig. 33.3 pg. 519)


Where these force lines are Where these force lines are close togetherclose together, , the force is the force is strongstrong. Where the lines are . Where the lines are farther apartfarther apart, the , the force is weakerforce is weaker..


Electric ShieldingElectric Shielding:: Because of mutual repulsion, Because of mutual repulsion,

electrons move as far apart as electrons move as far apart as possible. On a hollow object, possible. On a hollow object, the interior will have NO the interior will have NO CHARGE OR FIELD. CHARGE OR FIELD. The force The force on a test charge inside a on a test charge inside a hollow sphere will cancel to hollow sphere will cancel to ZeroZero


On odd shaped On odd shaped objects, objects, the chargethe charge inside is still zeroinside is still zero, , but not uniform on but not uniform on the outside.the outside.


Electric Potential EnergyElectric Potential Energy::

Remember chapter 8 when you Remember chapter 8 when you lifted an object --- you did lifted an object --- you did workwork on on that object. that object. The same thing The same thing applies here.applies here.

A test charge has A test charge has

Potential Energy by Potential Energy by

virtue of its position.virtue of its position.


If the test If the test charge is “let charge is “let go”, the go”, the potential potential energyenergy will be will be transferred transferred into into kinetic kinetic energyenergy of of movementmovement..


Electric Potential = Electric Potential = Electric potential Electric potential energyenergy

ChargeCharge

1 Volt1 Volt = = 1 Joule1 Joule_____ _____ 1 Coulomb1 Coulomb

Note --- The Note --- The voltagevoltage of a balloon rubbed on your of a balloon rubbed on your head can be very high. But the head can be very high. But the electric potential electric potential energyenergy is low because of the is low because of the small amount of small amount of chargecharge..


Storage of Storage of EnergyEnergy::

Electrical energy Electrical energy can be stored in can be stored in a common device a common device called a called a capacitorcapacitor. .


A capacitor is a devise that A capacitor is a devise that has two plates separated by has two plates separated by a small distance and a small distance and connected to a battery.connected to a battery.

Note --- this can be a Note --- this can be a ShockingShocking experience if you experience if you are the discharging path !are the discharging path !

conceptual physics notes on chapter 33 electric fields & potential

Documents

field lines

small test charge

lines of force

force lines

hollow object

kinetic energy of movement

hollow sphere

odd shaped objects