Grade 9 Science Unit 3: Electricity · 2019-09-20 · •As you add more bulbs, the brightness of...
Transcript of Grade 9 Science Unit 3: Electricity · 2019-09-20 · •As you add more bulbs, the brightness of...
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Grade 9 Science
Unit 3: Electricity
Chapter 9: Circuits are designed to control the transfer of electrical energy.
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Series Circuits
•There is only one path for the current to travel.
•bulbs connected in series; when one goes out, they all go out.
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•As you add more bulbs, the brightness of the bulbs decreases. (voltage is affected)•Adding more bulbs increases the resistance thereby decreasing the total current in the circuit.
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Ex. Christmas lights
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Parallel Circuits
•A circuit with several different paths.
•Bulbs connected in parallel; when one goes out, the others are unaffected.
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•As you add more bulbs, the brightness is unaffected. (voltage is unaffected)
•Resistance does not increase.
•No current is created or destroyed only split up.
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•Adding resistors in parallel will decrease the total resistance. This will increase the total current leaving the battery.
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Series Circuit Parallel Circuit
# of Pathways
Effect of removing a load
Voltage drop
Current
Resistance
Connecting cells to form a battery
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Core
Lab A
cti
vit
y
Resi
stors
in S
eri
es
and P
ara
llel
pg.
300-1
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Series vs. Parallel CircuitsSeries Parallel
Flashlight:
V = I =
Lighthouse:lifespan
=
maintenance
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Technologies for Safe Use of
Electricity
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•Circuit Breakers
Act as a switch that can cut off all power coming in to your house.
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•Fuses
Contains a metallic conductor that
melts when
excessive
current heats
it up.
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•Grounding terminals
Allows excess current to flow in to the ground instead of giving you
a shock.
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Electrical Energy
•The ability to do work
•Measured in Joules (J)
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Electrical Power
•The rate of change in electrical energy•The rate at which work is done or energy is transformed.•Measured in Watts (W)
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Electrical Energy Costs
Depend on 3 factors:
1. Voltage drop
2. Electrical current
3. Time
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Power Rating
•A measurement of how much electrical energy an electrical device consumes for every second it is in use.
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Calculating Energy Consumption
E = energy transferred (J)
P = power (W)
t = time (s) E
tP
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Energ
y
Consu
mpti
on
Pg.
308
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Paying for Electricity
Power is measured in kW•h
Complete 9-2 B pg. 310
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Careers related to Electricity
•Electrician
•Photocopier technician
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Electrical Efficiency
Electrical energy may be converted to other forms such as:
1. Light2. Heat3. Sound
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Efficiency is the % of energy that is converted to a useful form.
Efficiency = useful energy output x 100
total energy input
Complete practice problems pg. 318
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EnerGuide Labels
•Details how much energy an appliance uses in a year and compares to otherappliances.
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Reducing Electrical Consumption
•Improve insulation of home•Turn off lights when not in use•Use energy efficient light bulbs•Air dry clothes when possible
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CO
RE S
TSE
“Ele
ctr
icit
y
Conse
rvati
on:
The N
ew
Tre
nd”
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Energy Generators
•Electrical generator (made up of a coil
of wire and
a magnet)
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Electrical Generating Stations
1. Hydroelectric
2. Thermal
3. Nuclear
See pg. 327
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Getting Power…
*Transformers are electrical devices that change voltage so that it can be used by homes. (120 V and 240V)
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Problems?
1. Safety
2.Cost of production
3.Degree of environmental impact
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Alternate Energy Sources
•Wind generators
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•Solar energy
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•Fuel cells
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Constraints to New Technologies
1. Cost
2. Availability of materials
3. Properties of materials
See pg. 330-4