Chapter 8 slideshow.notebooklushmanscience.weebly.com/uploads/2/3/5/3/23534300/... · 2018. 9....
Transcript of Chapter 8 slideshow.notebooklushmanscience.weebly.com/uploads/2/3/5/3/23534300/... · 2018. 9....
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Chapter 8 slideshow.notebook March 07, 2015
Sep 89:31 AM
Unit 3 Electricity
• Electric Current
• Circuit Diagrams
• Challenge
• Homework
Chapter 8:Ohm’s law describes the relationship of current, voltage, and resistance.
Mar 48:12 AM
Current Electricity
Current electricity : is when the electrons are controlled by moving along a path together.
What is voltage?
Electric Potential Energy: Stored electrical energy
Ex. A battery its electrons can do work after they leave the battery.
Electric Potential Difference (Voltage): The change in potential energy per charge.
Electrochemical cell: produces a supply of electric charge by using chemicals (a reaction occurs).
3 Parts:
2 electrodes: of different materials: often metals, an electrical conductor
1 electrolyte: often a salt, acid or base in solution, the electrolyte will conduct electricity
Lets make some!
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Chapter 8 slideshow.notebook March 07, 2015
Mar 148:44 AM
This is about the number of electrons that pass into a 100 W light bulb per second.
Is this the true number of electrons and protons?
Top of school desk
Coulomb: the unit of electric charge.
1 coulomb = 6.25 x 1018 electrons. (added or subtracted)
Coulomb
Mar 148:56 AM
Electric current (A):a flow of electric charge through an electrical conductor.
The ampere (A) is the unit used for current
This is like:two rivers of equal size and volume
The river that flows faster has more water molecules flowing past a given point such as a bridge. This is a higher current.
higher current
Electric current
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Chapter 8 slideshow.notebook March 07, 2015
Mar 148:57 AM
Electric circuit
Electric circuit: A complete pathway that allows electrons to flow.
Will transform electrical energy into other forms of energy.
Mar 1810:11 AM
Parts of an electric circuit:
1) source: Where a form of energy is converted to electrical energy
2) Electrical load: Takes Electric energy and converts it into other forms of energy
e.g: heat, light and sound
Electric circuit
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Chapter 8 slideshow.notebook March 07, 2015
Mar 1810:17 AM
3) Control/switch : Opens and closes the circuitTurns circuit on and off
4) Conductor : Wires made of good conductors conducts electrons around the circuit
Electric potential is provided at the source (batteries) and “used” by the circuit elements (lightbulb)
(a potential or voltage drop occurs)
Electric circuit
Mar 1810:25 AM
Activity
Set up a working circuit
Make the light bulb shine!
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Chapter 8 slideshow.notebook March 07, 2015
Mar 149:00 AM
Circuit Diagram Symbols
• Electricians often have to draw out a circuit
• Instead of drawing each part in detail, they
use simple symbols
Corrupt???
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Chapter 8 slideshow.notebook March 07, 2015
Mar 1810:28 AM
Circuit diagram symbols:
• bulb • cell • battery • wires • resistors • ammeter • voltmeter • open switch closed switch
Circuit Diagram Symbols
http://www.andythelwell.com/blobz/guide.html http://phet.colorado.edu/en/simulation/circuitconstructionkitdc http://articl319.com/shockwave/oz.htm
Mar 1811:49 AM
Questions
1. Label the following:
2. When the switch is opened, what happens to the electrons in the circuit?
3. Using the proper circuit symbols, draw and label a circuit that contains a single cell, a lamp, and a switch. Use arrows to indicate the flow of electrons.
4. Draw a circuit diagram for the circuit shown.
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Chapter 8 slideshow.notebook March 07, 2015
Apr 85:07 PM
Resistance
Resistance: Slows down the flow of electrons and transforms electrical energy.
Measured in ohm’s (Ω)
Example: lightbulb, resistor etc
What is more difficult?• Walking on sand• Walking on gravel• Walking on Snow • Walking through water
Why?
This is the same for resistors. Some objects are more difficult for electrons to pass through
Resistors: Used to control current or potential difference in a circuit.
http://phet.colorado.edu/en/simulation/batteryresistorcircuit
Battery and resistanceActivity:
Apr 85:09 PM
Resistance
Factors affecting resistance:
• Length: Electrons will take a longer time to pass through along wire (A long hallway will take longer to walk through)
• Diameter: The thicker the wire the more electrons can pass(the wider the hallway the more students can pass)
• Temperature: It is harder for electrons to move through a warm wire, easier through a cold wire
(the more excited and crazy running students in a hall (warm) the harder it will be to go to class)
• Type of material: Some material are good conductors of electrons, other are poor
(If the hallway was made of crazy carpet or lava it would be hard to travel)
• If you double the length of a wire, you will double the resistance of the wire.
• If you double the diameter of a wire, you will cut its resistance in half.
Question
http://phet.colorado.edu/en/simulation/battery-resistor-circuit
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Chapter 8 slideshow.notebook March 07, 2015
Apr 85:26 PM
Relationship of Voltage Resistance and Current
Ohms Law: The mathematical relationship comparing voltage (V), current (I) and resistance (R)
http://www.glencoe.com/sites/common_assets/science/virtual_labs/E14/E14.html
Voltage resistance and current sim: after ohms law calculation
Activity 2:
Questions:
1. Find the size of the resistor which would allow a current of 0.02A, when connected to an 8V power supply.
2. Calculate the voltage across a 300Ω resistor when a current of 0.004A flows through it.
400Ω
1.2V
http://phet.colorado.edu/sims/ohmslaw/ohmslaw_en.html
Apr 1010:16 AM
http://www.glencoe.com/sites/common_assets/science/virtual_labs/E14/E14.htmlhttp://phet.colorado.edu/sims/ohms-law/ohms-law_en.html
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Chapter 8 slideshow.notebook March 07, 2015
Apr 1010:17 AM
Apr 84:17 PM
http://phet.colorado.edu/en/simulation/circuitconstructionkitdc
Labs
Conclusions
Homework: Ohm's Law worksheet
http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc
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Chapter 8 slideshow.notebook March 07, 2015
Sep 89:31 AM
Using the proper circuit symbols, draw and label a circuit that contains: a three cell battery, a lamp, and a closed switch. Use arrows to indicate the flow of electrons.
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