ElectricityElectricity

Electric Charge and Force Electric Charge and Force Electric ChargeElectric Charge- electrical property of matter - electrical property of matter

that creates a force between objects.that creates a force between objects.Charges- 2 charges generated by a build-up of electrical Charges- 2 charges generated by a build-up of electrical

charge: positive (+) and negative (-). charge: positive (+) and negative (-).

Like charges repel and opposite charges attract.Like charges repel and opposite charges attract.

Net chargeNet charge- The total amount (sum) of - The total amount (sum) of charge on an object.charge on an object. When the + and – charges are When the + and – charges are equalequal, there is , there is

no net chargeno net charge. Whenever there is an . Whenever there is an imbalance in the # of + & e-imbalance in the # of + & e-, you have a , you have a net net electrical chargeelectrical charge. .

The difference in the number of + & e- is the The difference in the number of + & e- is the electrical charge value. + charged objects electrical charge value. + charged objects have more protons, - charged objects have have more protons, - charged objects have more e-.more e-.

The The CoulombCoulomb, C- the SI unit for , C- the SI unit for electrical charge is the electrical charge is the coulombcoulomb (1.6 x 10(1.6 x 10-19-19). e- & + have ). e- & + have exactly the same amount of exactly the same amount of charge:charge:

+ =1.6 x 10+ =1.6 x 10-19-19 e- = -1.6 x 10e- = -1.6 x 10-19-19

Because the amount of charge on Because the amount of charge on

an object depends on the # of + & an object depends on the # of + & e-, the net charge of a charged e-, the net charge of a charged object is object is ALWAYSALWAYS multiplied by multiplied by 1.6 x 101.6 x 10-19-19 C C

Conductors & Insulators- Conductors & Insulators- ConductorsConductors always allow charge to always allow charge to

flow. flow. InsulatorsInsulators restrict or limit the flow. restrict or limit the flow.

Objects can be charged by the Objects can be charged by the transfer of etransfer of e--s. Electrons transfer s. Electrons transfer easily from one atom to another, easily from one atom to another, thus they can transfer from one thus they can transfer from one material to another. This can occur material to another. This can occur with or without friction (rubbing). with or without friction (rubbing). Think of rubbing a balloon on your head, Think of rubbing a balloon on your head, then getting a balloon to stick to the wallthen getting a balloon to stick to the wall. .

Electric ForceElectric Force- force generated by the - force generated by the repulsion/ attraction between two or more repulsion/ attraction between two or more charged objects. It also holds atoms charged objects. It also holds atoms together and other molecules. Without together and other molecules. Without it… life would be impossible.it… life would be impossible.

Electrical force depends on Electrical force depends on chargecharge and and distancedistance of objects. The more charge each of objects. The more charge each object has the stronger the electrical force. object has the stronger the electrical force. The further away the objects are, the weaker The further away the objects are, the weaker the electrical force becomes.the electrical force becomes.

Electrical force acts through a Electrical force acts through a field. An electric field is field. An electric field is generated around a charged generated around a charged object due to its charge. object due to its charge.

(electric field lines leave + charged particles (electric field lines leave + charged particles e.f.l. are attracted to – charged particles.)e.f.l. are attracted to – charged particles.)

E. F. L.- point in the direction E. F. L.- point in the direction of the electric force and help of the electric force and help define the electric field. define the electric field. ELECTRIC FIELD LINES ELECTRIC FIELD LINES NEVER CROSS! Positive NEVER CROSS! Positive electric field lines repel each electric field lines repel each other. The # of field lines other. The # of field lines reflects/indicates strength of reflects/indicates strength of charge. charge.

CurrentCurrent

Voltage and CurrentVoltage and Current A. A. Electrical potential energyElectrical potential energy: Potential energy : Potential energy

of a charged object due to its position in an of a charged object due to its position in an electrical field.electrical field.

Potential differencePotential difference: is the charge of the : is the charge of the electrical potential energy per unit of time.electrical potential energy per unit of time. occurs as a charge moves from one occurs as a charge moves from one

place to another in an electrical field.place to another in an electrical field.

VoltageVoltage -SI units for potential difference -SI units for potential difference measure in volts, V -equal to one joule measure in volts, V -equal to one joule per coulomb (1J/C).per coulomb (1J/C).

voltage exists across the terminals of a voltage exists across the terminals of a battery (1.5 V to 12 V). These batteries battery (1.5 V to 12 V). These batteries are called cells.are called cells.

CurrentCurrent - the rate that electric charges - the rate that electric charges move through a conductor.move through a conductor.

Electrical ResistanceElectrical Resistance A. A. ResistanceResistance: the ratio of the voltage : the ratio of the voltage

across a conductor to the current it carries. across a conductor to the current it carries. In other words how much electric power In other words how much electric power can it carry?can it carry? Resistance formula: Resistance formula: Resistance = voltage/current Resistance = voltage/current oror R= V/I. R= V/I.

Units ohm ΩUnits ohm Ω

B. Conductors have low resistances.B. Conductors have low resistances. C. A resistor is an C. A resistor is an insulatorinsulator, any material or , any material or

solution that does not allow the flow of solution that does not allow the flow of electrons. In other words they have high electrons. In other words they have high resistance resistance

Circuit symbols and Circuit diagramsCircuit symbols and Circuit diagrams