ELECTRICITY----STATIC AND CURRENT

What is happening in these pictures?

STATIC ELECTRICITY

A BUILD UP OF CHARGE( electrons ) from one object to another, without a flow of charge.

3 ways to create static electricity:

1.conduction: build up of charge by direct contact between 2 objects

Van de graph machine

2. Induction: build up of charge by force of attraction or repulsion WITHOUT touching one object to the other ( through open space )

Balloon Demo with Salt ( sugar ):

An electroscope demonstrates induction

Static electricity by friction

3. Friction: build up of charge by rubbing one object against another.

Rubbing hair with balloon

Static friction- study jams

• http://studyjams.scholastic.com/studyjams/jams/science/energy-light-sound/electricity.htmhttp://studyjams.scholastic.com/studyjams/jams/science/energy-light-sound/electricity.htm

Write the letter that most applies for each word. 

1.___ Repel A. Objects with opposite charges come together.

2.___ Electroscope B. Detects charges.3.___ Attract C. Objects with like charges jump

apart.

Answer the questions.State the Law of Electric Charges: _______________________________________  ____________________________________List the three ways in which an object can become charged:5) 6) 7) 

When an object becomes charged, one object ________ electrons, and one object _______ electrons.

multiple choice: _____ Electric force is found between a) Charged objects b) credit cards c) criminals _____ The area around a charged particle that can exert a force is called :a) electric force b) electric shock c) electric field 11. ______ The build up of electric charges on an object is

a) current electricity b) static electricity c ) electric discharge

Use the word bank to select your BEST answer.

FRICTION (f) INDUCTION (i) CONDUCTION (c) 12._____Electrons transferred from one object to another by direct contact. 13.____ Charges on an object rearrange without direct contactwhen a charged object is near it. 14. ____Rub 2 objects together. The electrons are transferred. 15. ____Rub a balloon on a wool sweater, and place it near a wall. 16. ____ Walking across a carpet.

E. True /False. CORRECT the False!!

17.____ A lightning bolt is an example of electric discharge. 18.____ An electroscope can tell if the charge is pos. or neg. 19.____ Static electricity is NOT as noticeable in the summer because of the dryness in the air. 20._____ Lightning is a result of the negative charges in the clouds being attracted to the negative charges on the ground.

http://phet.colorado.edu/en/simulation/balloons2011 electricity.ppt

Lightning video

• http://player.discoveryeducation.com/index.cfm?guidAssetId=5AE05296-1087-4C59-A5B9-4585869125DC&blnFromSearch=1&productcode=US

Ice hockey simulation

• http://phet.colorado.edu/en/simulation/electric-hockeyhttp://phet.colorado.edu/en/simulation/electric-hockey

Current electricity• Current is a flow of electric charges. It is not a build up of

charge that is discharged.

• All current elec. needs a circuit—a pathway for electric charges to flow..

• All circuits must have at least 3 parts : 1) wires, 2) a source and 3) a load(s).

Parts of a circuit

wires Source of electricity

Load

Conductors

• Conductor: a material that easily allows the flow of electric charges.

• It gives very little resistance to the flow of charge. ( metals – copper, aluminum , etc )

Insulators

• Insulators: do not easily allow for the flow of electric charges through them.

• Ex: glass, plastic, certain rubber materials, cloth.

Current electricity– brain pophttp://www.brainpop.com/technology/e

nergytechnology/currentelectricity/• http://www.brainpop.com/technology/

energytechnology/currentelectricity/

Types of circuits

• http://www.brainpop.com/science/energy/electriccircuits/http://www.brainpop.com/science/energy/electriccircuits/

Law of electric Charges

• Like Charges repel; Unlike charges attract.

2 main types of circuits

• 1. Series Circuit: only 1 path for the electric charges to flow

• 2. Parallel Circuit: has More than one path for the electric charges to flow.

Series circuit

Now, let’s draw it in your notes:

Resistance

• This is what “slows down” the movement of the electric charges … so they hit each other more…

• What do you think could ADD resistance in a circuit ?

• Add more loads to the same circuit• Heat• Longer wires• Thinner wires

Circuit Mini Lab• Take a sheet of computer paper. • You have 4 drawings, 4 circuits to build, and 4

questions to answer… Let’s do the drawings together, then you can build, and answer the questions:

• You Label: wires, source, load, direction, terminals, switch

• 1. 3.

• 2. 4.

2. Parallel Circuit: has more than 1 path for electric charges to flow, so if 1 load goes “out,” the other loads will still work !

Draw a parallel circuit

Circuit simulation

http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc

Alternating Current - AC• Electric charges move back and forth—homes

and buildings.Ex: 60 V one way and 60 V the other way,= 120 Volts

Let’s recap: • 2 types circuits 2 types current direction

Series Direct current 1 way

Parallel Alternating current Back and forth

Direct with a battery One way

BATTERIES • Electrolytes- liquids/acids that cause a chem. reaction, that releases electric charges

• Batteries (usually) are DC-direct current- where the electrons flow only in 1 direction.

CONVERT CHEM. ENERGY TO ELECTRICITY. 2 TYPES: A)DRY CELLSB)WET CELLSDry cells have paste-like electrolytes, and these are the batteries you are used to using. Wet cells have liquid electrolytes. ( car batteries)

Wet celldry cell

Inside a dry cell

Inside a wet cell

http://phet.colorado.edu/en/simulation/battery-voltagehttp://phet.colorado.edu/en/simulation/battery-voltage

Watch the stick figures move the charges Back and forth, creating a potential difference In voltage, making current !

Circuit breakers and fuses

• Circuit breakerCircuit breaker-open a circuit to keep from Overload.

Plug fuses

fuses

CURRENT RESISTANCE VOLTAGE

SYMBOL: IUNITS: Amperes

R or OHM’S

V

VoltsWHAT IS IT?The # of electrons. the rate at which charges pass a given point

The opposition to the flow of electrons; High resistance has more opposition to the flow4 THINGS THAT AFFECT R:Thin/thick wiresTemperatureLength WireType of wire-Copper-good conductor; decrease R; Iron- poor conductor; increase R

The energy of each electron.

Low voltage = little energy.High Voltage = High energy

More electrons=more current; less electrons = less current

↓ Thickness = ↑ R ↑ Temperature =↑ R ↑ Length = ↑ R

Ohm’s law

I = V/ R

Current = voltage/ resistance.

•Discuss wires and resistance!!

•What current would flow through a resistor of 20 ohms connected to a 12 V supply?• [A] 240 A • [B] 1.66 A • [C] 0.67 A • [D] 0.067A

What current would flow through a resistor of 40 ohms connected to a 10 V supply?• [A] 400 A • [B] 4 A • [C] 0.25 A • [D] 0.025A

A 100 ohm resistor is connected to a 20 V supply. What current flows?• [A] 0.02 A • [B] 0.05 A • [C] 0.2 A • [D] 0.5 A • [E] 2000 A

What value of resistor would be used to permit a current of 0.2 A to flow using a 6V supply?• [A] 0.03 ohms • [B] 0.3 ohms • [C] 3.0 ohms • [D] 30 ohms • [E] 300 ohms