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/ja ms/science/energy-light sound/electricity.htm

http://studyjams.scholas

tic.com/studyjams/jams/science/energy-light sound/electricity.htm

Write the letter that most applies for each word .

1.___ Repel 2.___ Electroscope 3.___ Attract A. Objects with opposite charges come together.

B. Detects charges.

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

FRICTION (f) Use the word bank to select your BEST answer.

INDUCTION (i) CONDUCTION (c)

12._____Electrons transferred from one object to another by direct contact.

13.____ Charges on an object rearrange without direct contact when 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/ballo ons2011 electricity.ppt

Lightning video

• http://player.discoveryeducation.com/index.cf

m?guidAssetId=5AE05296-1087-4C59-A5B9 4585869125DC&blnFromSearch=1&productco de=US

Ice hockey simulation

• http://phet.colorado.edu/en/simulation/elect ric hockey http://phet.colorado.edu/en/simulatio n/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).

Load

wires

Parts of a circuit

Source of electricity

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 pop http://www.brainpop.com/technology/e nergytechnology/currentelectricity/

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

Types of circuits

• http://www.brainpop.com/science/energy/ele ctriccircuits/ http://www.brainpop.com/scienc e/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/circu it-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 1 way Series Direct current Parallel Alternating current

Direct with a battery

Back and forth

One way

BATTERIES

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

dry cell Wet cell

Inside a dry cell

Inside a wet cell

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

http://phet.colorado.edu/en/simulation/batte ry voltage http://phet.colorado.edu/en/simulati on/battery-voltage

Circuit breakers and fuses

Circuit breaker-open a circuit to keep

•

from Overload.

Circuit breaker

Plug fuses fuses

CURRENT SYMBOL :

I

UNITS:

Amperes

WHAT IS IT?

The # of electrons. the rate at which charges pass a given point

More electrons=more current; less electrons = less current RESISTANCE

R or OHM’S The opposition to the flow of electrons; High resistance has more opposition to the flow 4 THINGS THAT AFFECT R:  Thin/thick wires  Temperature  Length Wire  Type of wire Copper-good conductor; decrease R; Iron- poor conductor; increase R ↓ Thickness = ↑ R ↑ Temperature =↑ R ↑ Length = ↑ R

VOLTAGE

V Volts The

energy

of each electron. Low voltage = little energy.

High Voltage = High energy

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