ElectricityElectricityElectricity

PolarityPolarity

N S NS

N SNS

LIKES LIKES REPEL!REPEL!

N S N S

OPPOSITES OPPOSITES ATTRACT!ATTRACT!

SAME RESULT WHEN DEALING WITH ELECTRICAL CHARGESSAME RESULT WHEN DEALING WITH ELECTRICAL CHARGES

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Cathode Ray Tube Cathode Ray Tube ExperimentExperiment

Firing charged particles

Vacuum tube filled with Vacuum tube filled with inert gas (does not react!)

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What did this prove?What did this prove?► What is the charge of the particle?What is the charge of the particle?

NegativeNegative Opposites attract!Opposites attract!

► What is the mass of the particle?What is the mass of the particle? Had a smaller mass than a hydrogen atom Had a smaller mass than a hydrogen atom Concluded that it is one of the particles that Concluded that it is one of the particles that

make up an atom!make up an atom! The tiny, negative The tiny, negative ELECTRONELECTRON was was

discovered!discovered!

Charges in ObjectsCharges in Objects► Under normal Under normal

circumstances, substances circumstances, substances have a neutral charge have a neutral charge

► But charges have the But charges have the ability to move around ability to move around creating a creating a charge charge differentialdifferential

Electric potential-voltage

Electric PotentialElectric Potential►

Electrons can be Electrons can be moved “UP” to moved “UP” to give them give them potential – potential – voltage. voltage.

► This requires This requires energy.energy.

► They can then be They can then be allowed to come allowed to come “down” using the “down” using the energy stored in energy stored in them.them.

Energy put Energy put in!in!

Energy Energy released!released!

Energy Energy stored!stored!

Generator: voltage and Generator: voltage and currentcurrent

Gas powered turbine Gas powered turbine that “pushes” that “pushes” electrons. This electrons. This

pressure is called the pressure is called the voltagevoltage; measured in ; measured in

voltsvolts..

The number of electrons in motion per second is called the current; measured in amperes

(amps).

1 amp physically means 1 amp physically means that 6.24 that 6.24 E18E18 electrons electrons move through a wire move through a wire

every secondevery second

Voltage, Current and Electricity Voltage, Current and Electricity usedused

► If you live in the If you live in the United StatesUnited States, the power outlets in the , the power outlets in the wall of your house or apartment deliver 120 volts each.wall of your house or apartment deliver 120 volts each.

► electricity consumedelectricity consumed (measured in watts) = amps x (measured in watts) = amps x volts volts Energy = # electrons x how fast they are being Energy = # electrons x how fast they are being

“pushed”“pushed”► Example: space heater. Example: space heater. You measure the amount of You measure the amount of

current flowing from the wall current flowing from the wall outlet to the heater, and it outlet to the heater, and it comes out to 10 amps. How comes out to 10 amps. How many watts does the heater many watts does the heater

use?use?

? volts? volts

120 v120 v10 10 ampsamps

xx

1200 watts1200 watts

Light Bulbs!Light Bulbs!

►Watts = amps x volts: Watts = amps x volts: This holds true for any This holds true for any electrical appliance. electrical appliance.

► If you plug in a light If you plug in a light and it draws half an and it draws half an amp, it's a __________ amp, it's a __________ light bulb.light bulb.

60 watt!60 watt!??

0.5 0.5 ampsamps== xx 120v120v

Light Bulbs #2Light Bulbs #2

If you plug in a 30 If you plug in a 30 watt light bulb and watt light bulb and it draws 0.25 amps, it draws 0.25 amps, how many volts is how many volts is the outlet?the outlet?

30 watt!30 watt!

30 watt30 watt 0.25 0.25 ampsamps== xx ? v? v

120 v120 v

CircuitsCircuits►The source of electricity must have:The source of electricity must have:

A positive terminalA positive terminal A negative terminalA negative terminal

►The source will want to push The source will want to push electrons out of its negative electrons out of its negative terminal at a certain voltage. terminal at a certain voltage. Ex: one AA battery wants to push Ex: one AA battery wants to push

electrons out at 1.5 volts. electrons out at 1.5 volts.

►The electrons flow from the The electrons flow from the negative terminal positive negative terminal positive terminal through a conductor terminal through a conductor (copper wire). (copper wire).

Electric Electric CircuitsCircuits

Circuit not closed

No battery!

Circuit complete

Series CircuitsSeries Circuits

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-Path of

electrons+ + +

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- - -

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Parallel Parallel CircuitsCircuits

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-Path of electrons

+ +- -

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►Battery: Battery: power sourcepower source

►Switch:Switch:Opens/closes Opens/closes

circuitcircuit

►LightLight

►MotorMotor

►Capacitor:Capacitor:Stores electricityStores electricity

►Fuse:Fuse:Safety: ”blows” with Safety: ”blows” with

electrical surgeelectrical surge

►Resistor: Resistor: Restricts flow of Restricts flow of

electricity electricity

Circuit symbolsCircuit symbols

M

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Smallest and Smallest and lightest!lightest! Nobel Gases!Nobel Gases!

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Cathode Ray Tube Cathode Ray Tube ExperimentExperiment

Firing charged particles

Vacuum tube filled with Vacuum tube filled with inert gas (does not react!)

+