1. Electricity
SCIENCE 9

2. A Shocking Experience
Electric charges – charged particles that exert a force on each other Complete the following chart in your notes:
Material
Prediction
Result
Two rubbed balloons (rubbed sides together)
Two rubbed balloons (turn one rubbed side away from the other balloon)

3. Electrically Charged particles
All matter is made up of particles called atoms
Each atom has subatomic particles called:
Protons – positive charge
Electrons – negative charge
Neutrons – no charge (neutral)
The protons and neutrons are found in the nucleus of the atom
The electrons are found outside the nucleus in the energy levels

4. Static electricity
Objects become charged when electrons move from one object to another
The electric charge that builds up on the surface of the object is called static electric charge
The charges are “static” because they do not move until they are given a path to escape
Objects can be charged by friction:
Different substances have different abilities to hold on to electrons. This is called electron affinity.

5. Laws of attraction and repulsion
Particles with opposite charges attract each other
Particles with like charges repel each other

6. Conductors and insulators
An insulator is a solid, liquid, or gas that resists or blocks the flow of electrons
Examples: dry wood, glass, plastic
A conductor is a material that allows the flow of electrons
Examples: copper aluminum
Semi-conductors allows some movement of electrons
Examples: water, human body, soil
Which picture best represents a conductor?

7. Transfer of Static Electric Charges
An electroscope can be used to test whether an object has been charged
The electroscope was invented in by a French scientist named Jean Nollet

8. Charging by Contact
Charging by contact occurs when electrons transfer from a charged object to a neutral object that it touches

9. Charging by induction
Charging by induction occurs when electrons transfer from a charged object to a neutral object without touching it.
Grounding is the process of connecting a charged object to the Earth’s surface. This creates a path for charges to get to the ground.

10. Electrical Discharge
An electrical discharge happens when electrical charges are transferred very quickly.
Lightning is one of the most spectacular examples of electrical discharge.

11. Electrostatic Generators
The Van De Graaf generator creates charge through friction
Charge is transferred from friction between the roller and belt and then transfer to the large metal sphere.

12. Lightning in First Nations Culture: The Thunderbird
In Metis and First Nations culture the thunderbird is a powerful weather controlling spirit. The thunderbird is found in most of the legends and stories told by Native American people all across North America.

13. Current electricity
Current electricity is electricity that flows through a circuit or pathway.
The flow of current electricity requires an energy source like a battery or some type of fuel
An electric circuit is made up of 4 parts:
Energy source
Conducting wires
Switch
Load

14. Complete circuit
Complete Circuit - A circuit that has a power source, a load (anything that uses electricity) and a ground point.

15. Closed Circuit
Closed Circuit – A circuit where energy flows from an energy source to the desired endpoint of the circuit.

16. Open Circuit
Open Circuit – An incomplete circuit in which no energy flows.

17. Series vs. Parallel Circuits
Series Circuit Parallel Circuit
-All components are connected in a line
-All components are connected in a parallel
fashion

18. Units of electricity
Voltage (V) – Electrical potential difference. Simply, how much electricity is in a circuit. Measured in Volts. Current (I) – The flow of electric charge. Measured in Amps. Resistance (R) – The repulsion of a current within a circuit. Measured in Ohms. - If a wire is long and small in diameter it will have a higher resistance - If a wire is short and larger in diameter it will have a lower resistance

19. I = V R V = IR R = V I Ohm’s Law
I = current (amperes, A) V = potential difference (volts, V) R = resistance (ohms, Ω)
I = V R
V = IR
R = V I
Example: A CD player uses a standard 1.5 V battery. How much resistance is in the circuit if it uses a current of 0.01 A?

20. Ohm’s Law Practice
What current flows through a hair dryer plugged into a 110 Volt circuit if it has a resistance of 25 ohms?
A 12 Volt car battery pushes charge through the headlight circuit resistance of 10 ohms. How much current is passing through the circuit?
An electric heater works by passing a current of 100 A though a coiled metal wire, making it red hot. If the resistance of the wire is 1.1 ohms, what voltage must be applied to it?
A subwoofer needs a household voltage of 110 V to push a current of 5.5 A through its coil (circuit). What is the resistance of the subwoofer?
A light bulb has a resistance of 5 ohms and a maximum current of 10 A. How much voltage can be applied before the bulb will break?

21. Calculating energy Energy = Power x Time E = P x T
Kilowatt hours = kilowatts x hours
kWh = kW x h
Example: If the power used by a microwave is 0.8 kW, and the microwave is used for 30 minutes, what is the total energy usage?
               E = ?       P = 0.8 kW           T = 0.5 h
               
                E = 0.8 kW x 0.5 h
                E = 0.4 kWh

22. The Cost of Electrical energy
Total Cost = Price x Energy
TC = Price x E
Example: If Saskatoon Light and Power charges 13.2 cents per kWh, how much will it cost to use a 350W blow dryer for a total of 19 hours in a month?
E = PT
E = kW x 19 h
E= 6.65 kWh
TC= Price x E
TC = ($0.132) (6.65 kWh)
TC= $0.88

23. Transformations of energy
What other kinds of energy can electricity transform into?
Why is efficiency less than 100%?
It uses energy to transform energy! Heat can be lost as heat (light bulb) or due to friction, etc…

24. Calculating the cost of electricity
Cost = Power x Time x Rate
Example: The average refrigerator uses 540 W per hour. If electricity costs $0.05 per kilowatt-hour (1 kW = 1000 W), how much would it cost to run the fridge for the month of January?

25. Calculating cost practice
A typical light bulb is 60 watts (therefore it uses 60 watts per hour). If electricity costs $0.08 per kilowatt-hour, how much would it cost to leave the light bulb on for three and a half hours?
2) a) An average computer uses 70 watts in an hour and a monitor uses 80 watts. How much would it cost to use the computer for 2 hours if electricity cost $0.12 per kilowatt- hour?
b) An LCD monitor uses only 35 watts per hour. How much money would you save in
the two hours if you used an LCD monitor instead of a regular one?
In 2011 Louisiana had the highest average annual consumption of household energy at 16,176 kWh and the average cost for energy was $0.10/kWh. In 2011, how much did the average home pay for electricity for the entire year and per day?

26. How can we reduce our consumption?
Use energy efficient appliances
Use energy efficient light bulbs
Turn off the lights when you leave a room
What else?