# Electric Charge and Static Electricity ELECTRICITY----STATIC AND CURRENT 31, 2012 Objectives: Describe how charged objects interact by using the law of.

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Electric Charge and Static Electricity ELECTRICITY----STATIC AND CURRENT 31, 2012 Objectives: Describe how charged objects interact by using the law of electric charges. Describe one way in which an object can become charged. Do Now: What are the parts of an atom? Do you know? Homework: Energy Project Due tomorrow!!! Make sure you email it to me by class tomorrow or it will be late!

Section 1 Electric Charge and Static Electricity Chapter 17

Law of Electric Charges Like charges repel; Opposite charges attract

Section 1 Electric Charge and Static Electricity Electric Charge  Electricity is the energy caused by the flow of electrons.  Charges Exert Force Atoms are composed of particles with electric charge.  The law of electric charges states that like charges repel and opposite charges attract. Chapter 17

Section 1 Electric Charge and Static Electricity Electric Charge, continued  The Force Between Protons and Electrons Because protons and electrons have opposite charges, they are attracted to each other.  The Electric Force and the Electric Field The force between charged objects is an electric force.  An electric field is the region around a charged object in which an electric force is exerted on another charged object. Chapter 17

What is happening in these pictures?

March 5, 2013 Do Now: Using the Law of Electric Charges, predict what will happen: – A B C 1.Between A & B? 2.Between B & C? 3.Between A & C? Objective: define static electricity and describe the 3 ways an object can become charged! Homework: Go to Mrs. Anicito’s page and open the lightning assignment. Complete for Thursday! + + _

Charge and Static Electricity Chapter 17  Static Electricity : A BUILD UP OF CHARGE (electrons) on an object!  Electric Discharge: loss of static electricity  Detecting Charge You can use a device called an electroscope to see if something is charged.

Electric Charge and Static Electricity Charge It!  Friction Charging by friction happens when electrons are “wiped” from one object onto another.  Conduction Charging by conduction happens when electrons move from one object to another by direct contact.  Induction Charging by induction happens when charges in an uncharged metal object are rearranged without direct contact with a charged object. Chapter 17

Static electricity by friction 1. Friction: build up of charge by rubbing one object against another. Rubbing hair with balloon

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

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

Study Jams - Electricity

3 Ways to Charge an Object

Use the word bank to select your BEST answer. FRICTION (f) INDUCTION (i) CONDUCTION (c) 1._____Electrons transferred from one object to another by direct contact. 2.____ Charges on an object rearrange without direct contact when a charged object is near it. 3. ____Rub 2 objects together. The electrons are transferred. 4. ____Rub a balloon on a wool sweater, and place it near a wall. 5. ____ Walking across a carpet.

Write the letter that most applies for each word. 1.___ RepelA. Objects with opposite charges come together. 2.___ ElectroscopeB. 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

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.

Lightning video http://player.discoveryeducation.com/index.cf m?guidAssetId=5AE05296-1087-4C59-A5B9- 4585869125DC&blnFromSearch=1&productco de=US http://player.discoveryeducation.com/index.cf m?guidAssetId=5AE05296-1087-4C59-A5B9- 4585869125DC&blnFromSearch=1&productco de=US

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

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 currentBack 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 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)

Wet cell dry cell

Inside a dry cell

Inside a wet cell

http://phet.colorado.edu/en/simulation/batte ry- voltagehttp://phet.colorado.edu/en/simulati on/battery-voltagehttp://phet.colorado.edu/en/simulati on/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 breaker Circuit breaker-open a circuit to keep from Overload. Plug fuses fuses

CURRENT RESISTANCE VOLTAGE SYMBOL : I UNITS: Amperes R or OHM’S V Volts WHAT 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 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 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

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