Download Sci 9 ELECTRICITY PAT Review

Sci 9 ELECTRICITY Review
(using 2010 released test questions at www.questaplus)
 FACTS ABOUT ELECTRICITY (Topic 1) #1, 9, 11
• electricity is the flow of electrons.
• Electricity occurs in 2 ways: 1) Electrical currents: this is electricity that can run things (like
flashlights, toys, lights, motors), and 2) Unbalanced charges: static electricity (where the
unbalanced electrical charges don’t move –like rubbing a balloon on your hair) or electrical
discharges like lightning. In electrical discharges the electricity builds up so we get such unbalanced
charges they move to discharge the electrical imbalance.
 CIRCUIT DIAGRAMS (Topic 2) - Series vs Parallel Circuits #4,7, 9, 10, 14, 15
• Parallel- set up like railroad tracks so set up at least 3 tracks, all light bulbs in the circuit are the
same brightness because the same amount of current goes in each “track”, and if one bulb
breaks the others still light. Series – as you add light bulbs they dim because they have to share
the current, and if one light bulb breaks none of the others will work because the circuit is now
broken.
• Bulbs light because of resistance (friction) to electron movement in the wires:
• 4 parts to a circuit – conductors, switch, power source (battery or generator), load
• Voltage (V) = potential difference,
measured with voltmeter.
• Current (I) = electron flow, measured
with ammeter
 Electricity Calculations (Topic 3, 7)
E = Pt
R=

V
I
#8, 17, 20 NR 1, NR 2
E = energy in Joules (J) P = Power in watts (w)
R = resistance in ohms (Ω)
V = voltage in volts
t = time in seconds
I = current in amps
What reduces resistance in an electric circuit? Increasing diameter of wires, use a wire that is a
better conductor, decreasing the wire length
Energy Conversions: 1KJ = 1 kilojoule = 1000 J or 1.0 x 103 J
1 MJ = 1 megajoule = 1000000 J 0r 1.0 x 106 J
Efficiency =
EO
x 100
EI
EO = energy output
EI = energy input
 MRS CHEN AND TRANSFORMATIONS IN ELECTRICITY (Topic 4) #13,

thermocouples
(heat energy to electricity) , piezoelectric effect (motion to electricity), batteries
(chemical energy to electricity), solar (light to electricity)
 Electrochemical Cells (batteries) (Topic 5) #6, 12
Battery is made of 2 electrodes of 2
different metals, electrolyte (charged
particles – ions, acids, bases) in middle. Also
called wet and dry cells
 Electromagnets, generators, motors (Topic 6) #19
How do you increase the strength of an electromagnet? Put more electricity running around
magnet by adding more wire coils or increasing the current running through the wire, use a wire
with less resistance which increases current running through wire, use a larger iron core (more
iron to magnetize). #3
 How is electricity generated for the world: (Topic 8) #5, #16
• renewable (biomass, wind, hydro)/nonrenewable (fossil fuels) electrical energy source