- Physics - Approximately April 28 th to May 16 th

- Physics -

Approximately April 28th to May 16th

We will be discussing:

Electricity as a Fluid. (Accessed on 2014).

Uploaded by Dr. Dadiv Stern Available online at: http://www-spof.gsfc.nasa.gov/Education/welectrc.html

Embedded Hybrid Headphone (2007).

Uploaded by Cavalli Audio. Available online at: http://www.cavalliaudio.com/diy/ehha/images/BasicAmpSimpleSchematic.gif

The Energuide Label (2009).

Uploaded by Natural Resources Canada. Available online at: hhttp://198.103.48.133/publications/infosource/pub/appliances/2007/page2.cfm?attr=4

Your Experience with Atoms & Elements:

Grade 7 – Particle Theory of Matter

Grade 6 – Electricity/Circuits

Use the textbook to review/learn important vocabulary

Bill Nye Electricity

https://www.youtube.com/watch?v=ugtHMtc08DM

Plutarch Model

- The “Air Model”

- Charged objects heat the air around them- Swirling air pushed

nearby objects towards it

- Challenges? Previous Models of Static Electricity. (Accessed on 2014). Uploaded by SJSD. Available online at: http://www.sjsd.net/~bhayward/Unit%203%20Electricity/2%20-%20Models%20of%20Static%20electricity%20(3-02,%2004).pdf

William Gilbert Model

- The “Sticky Hand Model”

- Thought a substance called Effluvium came from the charged object and attached to other objects

- Challenges? Previous Models of Static Electricity. (Accessed on 2014). Uploaded by SJSD. Available online at: http://www.sjsd.net/~bhayward/Unit%203%20Electricity/2%20-%20Models%20of%20Static%20electricity%20(3-02,%2004).pdf

Ben Franklin Model

- The “1-Fluid Model”

- All objects contain electric fluid

- If an object gains fluid it becomes positively charged

- If an object loses fluid it becomes negatively charged

Previous Models of Static Electricity. (Accessed on 2014). Uploaded by SJSD. Available online at: http://www.sjsd.net/~bhayward/Unit%203%20Electricity/2%20-%20Models%20of%20Static%20electricity%20(3-02,%2004).pdf

Charles Dufay Model

- The “2-Fluid Model”

- All objects contain electric fluids

- If an object gains or loses one of the fluids (+ or -), it will become charged


Particle Model

- Everything is made of atoms- Protons, Electrons, Nuetrons

- An object becomes negatively charged by gaining electrons

- An object becomes positively charged by losing electrons


Particle Model

- Charges are not created or destroyed, they are conserved

- When two materials come in contact, the valence electrons transfer from one material to the next


Persuasive Model Ad/Commercial

Groups of 3(boys & girls)

Understanding of Electricity Intro

Page 294

Qs 2, 3, 6, 7, 13

- An electricity current is the movement of an electric charge

- Involves the controlled movement of electrons

- For electrons to transfer, a conductor must be used to conduct the charge

How It Works- A charged object is brought towards

a conductor

- A charge separation is created on the conductor- Called polarization- Think of how one side of a battery

displays (+) and the other displays (-)

How It Works (Cont.)

- The charge builds up & can be released on a conductor in short bursts- It is not a continuous release of

electrons, just enough to keep it going

- Once all the charges are released, the current will stop

Electric Cells

- A type of device designed to produce electrical charges longer than what was previously possible with electrostatically-charged objects

(ex) Volta cells, dry cells, wet cells

Volta Cell/Wet Cell

- Two different metals were placed in a salt

or acid solution

- The chemical reaction caused sparks without being recharged

Volta Cell/Wet Cell

- The salt solution contains (+) Sodium Ions & (-) Chlorine Ions

- The Copper gives electrons to the (+) Sodium ions- Copper becomes

(+)

Volta Cell/Wet Cell

- The Zinc attracts the (-) Chlorine Ions- Zinc becomes (-)

- The conducting loop provides a path for the electrons to flow from the Zinc to the Copper

Dry Cells

- Same idea as a wet cell but uses a paste instead of an acid/salt solution- Smaller- Easier to handle/transport

Ways to Represent Circuits

- Words- A circuit containing three light bulbs & 3 AA

batteries

- Picture

- Schematic

Component Symbol Alternate

Cell (1.5V)

Battery (9V)

Wire

Resistor

Lamp Light Indicator

Switch Open Shut

Schematic Diagram Practice- Write & Switch -

Online PHET Lab

Measuring Electrical Current

- How many charges (electrons) past by a given point per unit time

- The coulomb is the unit used when measuring charge (C)- 6.25 x 1018 electrons


Current = coulomb/second

- Also known as an ampere (A)

- Commonly called amps


- Therefore, the formula utilized is:

I = Q/t- Where:

- I = electric current (A) ampere

- Q = charge (C) coulomb- t = time (usually seconds)

Math Breakdown

- List the given numbers (which variables do you have)

- What variable is the question asking you to find?

- Write down your formula- Solve using algebra- Remember units

Example One

- Given:Q = 0.15C t = 1s

- Calculate I

- What are the units for I?

Example Two

- A flashlight bulb has a label that reads 0.25A.

- How many coulombs of charge pass through the bulb in 1 second?

Measuring Electrical Potential

- Looks at the potential difference between the negative & positive terminals

- The coulomb or joule is the unit used when measuring potential- Called Volts

Measuring Electrical Potential

- A Volt = the energy of each charge- If there is more

charges, there is more total energy

- Energy = charge x Electrical Potential (volts)


- Therefore, the formula utilized is:

V = E/Q- Where:

- V = electric potential (V) volts

- E = energy (J) joules- Q = charge (Q) couloumbs

Example Three

- Given:E = 86JV = 9V

- Calculate Q:

Example Three

- How much energy can a toaster produce when it is plugged into a 110V outlet with a total charge of 25C passing through?

Current, Voltage, Resistance Worksheet

Electrical Devices

Used in a Week

EssentialVs

ExtraHrs/Week

Rank from “Uses

Most” to “Uses Least”

1

20

- Conductors emit energy in the form of heat or light- Due to resistance

- The “loss” of energy in the form of heat creates inefficiencies - Bad = light bulbs- Good = stove elements

- Power = how much energy is used in a certain amount of time

- The formula utilized for energy consumption (aka Power) is:

P = I x V

- Where:- P = Power (Watts)- I = Current (Amps)- V = Voltage (Volts)

Example One

- How much current does a 1500W hair dryer draw when plugged into an 110V household plug in?

- P = I x V

Example Two

- How much power is consumed by a 17 inch LCD screen that draws 1A at 110V?

- P = I x V

Example ThreeConsider the power rating of the following items:

Stove: 2000W Vacuum: 800 W TV: 200W Light Bulb: 60W Toaster: 900 W Microwave: 650W CD Player: 25 W

-A typical household circuit breaker is designed to allow a maximum of 15A on a 110 V circuit. - How much power can the circuit

handle?

Example Three (Cont)Consider the power rating of the following items:


-A typical household circuit breaker is designed to allow a maximum of 15A on a 110 V circuit. - Determine if the breaker will trip if the

toaster and microwave are both being used on the same circuit.

Example Three (Cont.)Consider the power rating of the following items:


-A typical household circuit breaker is designed to allow a maximum of 15A on a 110 V circuit. - Determine if the breaker will trip if the

vacuum, TV, and microwave are on.

Example Three (Cont.)Consider the power rating of the following items:


-A typical household circuit breaker is designed to allow a maximum of 15A on a 110 V circuit. - Can the stove be used on this circuit?

Example Four

- Would a stove that requires 2000W work on a 30A with 220V circuit?

- P = I x V

Example Five

- You have a 1500W hair dryer.- How many kilowatts (kW) would the hair dryer use?

- 1.5kW

- By the end of a 30 day month how many hours will it have been used if it is used for 3 minutes each day?- 90 mins or 1.5 hours

- If it costs $0.15 to use 1 kW for an hour. How much would it cost to operate the hair dryer for a month at 3 minutes each day. (Total = cost x kW x hrs)

Understanding Energuide. (2013). Uploaded by the Office of Climate Change. Available online at: http://www.turnbackthetide.ca/at-home/appliances/energuide.shtml#.U3IdU_ldWSo

Documents

- Physics - Approximately April 28 th to May 16 th