ELECTRICITY----STATIC AND CURRENT 31, 2012 Electric Charge and Static Electricity 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!

ELECTRICITY----STATIC AND CURRENT 31, 2012 Electric Charge and Static Electricity

ELECTRICITY----STATIC AND CURRENT 31, 2012 Electric Charge and Static Electricity 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

Electricity is the energy caused by the flow of electrons. Section 1 Electric Charge and Static Electricity Chapter 17 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.

Electric Charge, continued Section 1 Electric Charge and Static Electricity Chapter 17 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.

What is happening in these pictures?

March 5, 2013 Do Now: Using the Law of Electric Charges, predict what will happen: A B C Between A & B? Between B & C? 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! _ + +

Static Electricity : A BUILD UP OF CHARGE (electrons) on an object! 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 Chapter 17 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.

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.___ 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

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

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 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 1 way Direct current Series 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: DRY CELLS 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

Watch the stick figures move the charges Back and forth, creating a potential difference In voltage, making current ! http://phet.colorado.edu/en/simulation/battery-voltagehttp://phet.colorado.edu/en/simulation/battery-voltage

Circuit breakers and fuses Circuit breaker-open a circuit to keep from Overload. Plug fuses Circuit breaker fuses

Low voltage = little energy. High Voltage = High energy 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

Current = voltage/ resistance. Discuss wires and resistance!! 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