Unit 3: Electricity (Physics)
11.1 Introduction to Static Electricity
Static Electricity
•
All everyday objects are made of ____________ ,which contain ____________ and ____________
charges.
•
A ________________ object has an _________________ of protons ( ) and electrons ( ).
•
A __________________ charged object has _________________________.
•
A __________________ charged object has _________________________.
•
Static Electricity:
•
Is used in many everyday objects like
The Law of Electric Charges
What about Neutral Objects?
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Two neutral objects are __________________________________________________.
•
However, an _______________________________ can occur by bringing a charged object
__________________________________________________a neutral object, causing the electrons
to ______________________________ in the objects.
•
So, attraction or repulsion can occur between a ___________ object and a _____________ object.
Detecting Static Electrical Charges
Electroscope –
Two types: ___________________ electroscope
_________________ electroscope
11.2 & 11.6: Three Ways an Object Can be Charged
1. Charging By Friction

Two different _________ materials are _____________________________________ and
__________________________________from one object to another.

One material becomes ____________ charged, the other becomes____________ charged.

Some objects become charged ___________________ than others.
The Electrostatic Series

A list of materials arranged in order of their
_________________ to gain ______________.

When two materials are rubbed together, the
material ________ on the list becomes ___________
charged and the material ___________on the list
becomes ______________ charged.
Example: You rub wool on your skin. What charge does
each material have?
Example: You grab a rubber balloon with a wool glove
on your hand. What charge does each material now have?
Example: What happens when you rub your head with a
balloon?
2. Charging by Conduction (Contact)

Occurs when two objects come in _______________________ and the
____________________________ from one object to the other.

One material must start off being _____________. The other can be ______________ or
______________.

Electrons always move _____________the object with the __________ negative charge ______ the
object with the ____________ negative charge. The electron distribution _______________.
Grounding

______________________________________ electric charge than an object might have by
connecting it to a large body, like __________.

The Earth (ground) is so large, it acts like a _________________ for _________________. The
excess charge is spread over such a large area.

When a positively charged object is grounded, electrons ______________________________
__________________to neutralize the object.

When a negatively charged object is grounded, electrons _____________________________
_________________ to neutralize the object.

Symbol for grounding:
Example: What is a shock?
3. Charging by Induction (no contact)
-
When a _________________ object is brought _________a ______________ object, it causes (or
induces) the electrons to ________ in position, giving an __________ distribution of charges in the
objects.
-
When the charged object is taken away, the electrons _____________ to their original position.
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Electrons DO NOT _________________________! They only ________________.
-
If you _________________ the ______________ object during induction, you can
_______________________________________ the neutral object.
Example: a positively charged balloon is brought near a neutral hand.
11.4: Conductors and Insulators
Conductors
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Materials that
•
Ex:
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________________ and some _______________ like _________________________________ are
______________________________ (electrons flow , _________________________)
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We cannot place a charge on a conductor because the charge _____________________________
Insulators
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Materials that
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Ex:
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Electric wires (which are conductors) are coated with an ____________________ to protect us from
getting a _____________________________
Testing for Conductors and Insulators Using an Electroscope
Object
Does electroscope remain
charged?
Why do the leaves lower if the material is a conductor?
Why do the leaves remain raised if the material is an insulator?
Conductor or Insulator?
11.8: Electric Discharge
Electric Discharge

the

Sometimes seen as _______________

Some discharges are not painful, like

Other discharges can hurt, like ______________________

Can damage __________________________________________________
How does a car door shock you?
Lightning

Happens because of

___________________________ cause a build-up of static charges in clouds and water droplets
How Lightning Occurs:
1. ____________________________ collect at the______________ of the cloud.
2. These charges _________ the electrons at Earth’s surface, causing a ___________________ area near
the __________________________
3. If this charge imbalance is _______________________, the excess electrons in the clouds are
____________________________ to the ground, forming _____________________!!
Lightning Rods

Lightning can cause damage to structures and technology.

To prevent this, lightning rods are placed _________________________________
◦

provide a
Made of ____________, like iron or copper. Why?
12.1: Current Electricity
Current Electricity –

In static electricity, electrons __________________________, on the _________________ of an
object, and move ____________________________________
Forms of Current Electricity
Electron Flow
Production
Where is it Found
Other Information
12.2: Electric Circuits
Electric Circuit –
A simple circuit includes:
1.
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Provides the _________________ for the circuit
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Examples:
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A device that ____________________________________________________________________
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Examples:
2.
3.
•
4.
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Controls ______________________
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When the switch is on, the path is ____________, so electrons ________________
•
When the switch is off, the path is ___________, or disconnected, so the electrons ______________
•
Examples:
12.5: Generating Current Electricity
We get most of our electricity from wall outlets. But, where does that energy come from? How is it generated?
There are two types of resources that are used to generate electricity:
Non-Renewable Resources –
Renewable Resources –
1. Moving Water: Hydro-Electric Generation
Definition and Other Information
Pros
Cons
Pros
Cons
2. Moving Water: Tidal Generation
Definition and Other Information
3. Steam: Thermal Generation
Definition and Other Information
a. Burning fossil fuels
b. Using radioactive materials
Pros
Cons
Definition and Other Information
c. Using Biomass - burning plant or animal materials
d. Using Geothermal Energy - thermal energy deep
in Earth’s crust
Pros
Cons
4. Wind
Definition and Other Information
Pros
Cons
Pros
Cons
5. Light
Definition and Other Information
12.7 Electrical Power and Efficiency
Power
•
the rate at which _________________________________ or the rate at which _________________
Electrical Power
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The rate at which __________________________________________________________________
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Measured in __________________
▫
1 Watt is equal to _________________________________
▫
Watts are fairly small, so total energy usage is usually measured in _____________________
Conversion:
Formula #1
Formula #2
Example: Calculate the power of a toaster that used 72,000 J of energy in 1 hour. Use the GRASS method.
Percent Efficiency
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Electrical devices are not perfect
•
They do not convert all the energy into the __________________________
▫ ie: an incandescent light bulb: some energy is always converted to __________
▫ A CFL (compact fluorescent light bulb) produces much less heat, so it is __________________
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Efficiency –
•
The closer the value is to ________%, the _________________________ the device.
Example: A toaster oven used 1200 J of energy to produce 850 J of thermal energy. Calculate the percent
efficiency of the toaster oven. Use the GRASS method.
Cost of Electricity
•
There are different costs for electricity depending on ______________________________________
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Kilowatt-hour (________) – standard unit for measuring ____________________. Electricity meters
keep track of this information.
•
Currently in Brampton, the cost of electricity is:
per kWh (off-peak)
per kWh (mid-peak)
per kWh (on-peak)
To determine the cost to operate a device, use the equation:
**All units must be the same!!**
-- if cost is in $/kWh, what units should Power ________ and time _________ have?
Example:
How much money does it cost to operate a 240 W flat screen television for 13 hours? It is a rainy Saturday
and electricity is off-peak in Brampton.
Example:
How much money do you waste if you leave your computer on?
A computer can use up to 600 kWh of electrical energy a year if left on when not in use.
If you put it to sleep when not using it, it only uses 20 kWh of energy per year.
Assume the average cost of electricity is 8.1¢/kWh
13.1: Circuits and Circuit Diagrams
Circuit Diagrams

Type of
Component
Name of
Component
One-Cell Battery
Energy Source
Three-Cell Battery
110 V source
(wall outlet)
Connecting Wire
Connecting
Wires
Wires Joined
Ground Connection
Open Switch
Control
Devices
Closed Switch
Fuse
Light Bulb
Resistor
Electrical
Loads
Voltmeter
Ammeter
Ohmeter
Motor
Symbol
Function
Types of Circuits
Flow of Electrons
Position of Loads
Which way do electrons flow?
Drawing Series Circuits
Example 1:
Draw a circuit diagram showing an electric cell, a
switch, and one lamp. Show the flow of electrons.
Example 2:
Draw a circuit diagram showing a three-cell battery,
a switch, two lamps, and a fuse in series. Show the
flow of electrons.
What happens if you unscrew a light bulb?
Drawing Parallel Circuits
Example 3:
Draw a circuit diagram show a two-cell battery with
two lamps connected in parallel. Include a switch
for controlling each lamp. Show the flow of
electrons.
What happens if you unscrew a light bulb?
Example 4:
Draw a circuit diagram showing a 110 V source
with three lamps and a motor all in parallel. Include
a switch for controlling each load. Show the flow of
electrons.
13.3: Electric Current
Electric Current
•
•
Measured in ___________________, or ______
•
The symbol for current is _______.

▫
(ex:
).
because there are so many electrons involved in a circuit, they are ____________________
into a ______________________
1 COULOMB = _______________________________
Ammeter
•
Device that ___________________________________. Circuit symbol:
•
Must be connected in ______________________________________ to measure the current
flowing through the load.
▫
By doing this, we measure the amount of current that ________________ through the lamp.
▫
Match up ________________ side of the source with _______________ side of ammeter
Safety and Electric Current
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____________________________ can result if _______________ current is flowing through a circuit.
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Homes/buildings have either a ______________________ panel OR ______________
▫
If too much current is flowing through a circuit, these “trip” or “blow” to turn off the current – act
like ________________________
Current Calculations
Example 1: If 240 C of charge pass a point in a
Example 2: If the current flowing through a
conductor in 5.0 minutes, what is the current
conductor is 1.2 A, how much charge passes
through that point in the conductor? Use GRASS
through a given point in the conductor in 3.0 min?
13.5 Voltage (Potential Difference)
Voltage (Potential Difference)
•
•
HUH??? When electrons flow through a load, like a bulb, the bulb uses some of the energy. So, less
electrons come out of the bulb compared to what went in. The voltage is _______________________
__________________________________________
•
Unit and symbol is ___________________
ex: ___________________
Voltmeter
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Measures _______________
•
Must be connected ___________________________ with a load or an energy source
•
Symbol:
one end of the wire is positioned ____________ the load/source and the other end of the wire
is positioned __________ the load/source
•
Match _________________ end of meter to _______________ end of source
Voltage Calculations
Example: A battery contains 45 J of chemical energy that places 15 C of negative charge at the negative
terminal. What is the potential difference of the battery? Use GRASS.
13.7 Resistance in Circuits
Electrical Resistance
•
•
Symbol is ______
•
The unit is the ________
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Resistors create “____________” or “___________________” so that the electrons cannot flow as
easily through a circuit.
•
The______________ the resistance, the ____________ the current is, and the ____________ the
material becomes when current flows through it.
Resistors in Circuits
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Resistor – a device that
•
Circuit symbol:
•
Examples:
Measuring Resistance
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An ____________________ measures resistance.
•
Must be connected _____________________with a load.
▫
Circuit does not have to be on because
Factors that Affect Resistance
1.
•
_________________ let electrons flow ________________, so they have a _________resistance.
•
_________________ have a _________________ resistance
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Cutting a wire allows you to see its diameter.
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___________ wires have __________ resistance than ____________ ones.
2.
▫
Electrons in the thicker wire __________________________________________
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This is like _______________________ – the thicker the pipe, the ___________ the water flows.
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______________ wires have _________ resistance than _____________ wires.
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This is because
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Resistance ___________________ as temperature increases.
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This is because
3.
4.
Calculating Resistance
Example: A light bulb has a resistance of 10 Ω. What current flows through the bulb when it is connected to
a 120 V source of electrical energy? Use GRASS.
13.10: How Series and Parallel Circuits Differ
1. Current in Circuits
a) Series
b) Parallel
2. Voltage in Circuits
a) Series
b) Parallel
3. Resistance in Circuits
a) Series
b) Parallel
Summary
Quantity
Total Resistance of Circuit
Current through loads
Voltage across loads
Series Circuits
Parallel Circuits