Download Science 9 Current Electricity Notes 2012

Science 9
Current Electricity Notes 2012
Some Review:
What are the three subatomic particles and their charge?
Where are each of the three subatomic particles located?
•
Current Electricity: is a
source
•
Circuit:
•
flow of electrons from an energy
flow of
in a complete path
Circuits generally consist of four main components:
1)
2)
3)
4)
1
Conductors and Insulators:
•
Conductor – a material that
– Most
are conductors
Examples:

Insulator – a material that
- Most
are insulators
Examples:
•
Semiconductors are
have
semiconductors are used extensively to make computer microchips.
•
Superconductors are materials that offer
to the flow of electrons.
•
- they
to electron flow. Silicon
Examples:
•
Electricity can flow when it has a
•
A circuit is composed of an
and an
.
Measuring Current:
Measuring Current
• Ampere (
) – measure of the
passing a point each second
An instrument used to measure
called a
• Larger currents are measured with an
is
.
.
2
Ammeters in Circuits:
•
An ammeter is
the device)
(all current must flow through
Voltage:
•
•
Electrical energy is measured in
– aka
Voltage is a measure of
electrical energy each
charged particle carries. The higher the energy of each charged particle, the greater the
potential energy.
Voltmeters:
•
•
•
•
Voltmeter – a device to
(voltage)
Multimeter – a device that measures many characteristics of circuits including voltage
A voltmeter is connected
(to either side of a load to
measure
)
red to
(+) and black to
(-)
3
Did you know?
•
•
A current with an amperage as little as 0.1A is felt as a shock but a current of 1.0A is
deadly.

Resistance:
•
Resistance:
– Limits the
– Expressed in
– Affected by
• High
•
High
•
High
of electricity
and
means high
means low
means
resistance
Your Task:
•
Check & Reflect page 283 # 1 – 9
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Science 9
Electrical Safety Notes 2012
•
Voltage and amperage both play a role in whether electricity can kill
•
A significant electric shock, that is not fatal, can still cause serious and long term
damage or injury to your body and nervous system
•
Short Circuit: Current
normal circuit and takes the
route
– Downed power lines will allow the electricity to move outside the circuit
•
Two factors are at play with respect to the severity of electric shock
– Voltage
• 50,000 V is more likely to be fatal than 10 V
– Amperage
• Plays a bigger and important role
• 0.0001 A through your body would likely not be felt
• 0.015 to 0.020 A will cause a painful shock and will cause muscles to
clench
• 0.1 A can be fatal
•
Remember: Voltage Jolts, Amperage Kills
What should you do if you are driving and make contact with a power line?
Insulators and Conductors
•
•
Rubber soled shoes or car tires may provide some protection from a shock
Other substances may come into play, wet or damp soil will conduct better than dry soil
– Example if you touch an electric fence on a dry day, the shock will be less than
the same fence on a damp day with muddy ground
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Electrical Safety 101
•
Never handle electrical devices when you are wet or around water
•
Don’t use any power cord that is frayed
•
•
•
Always unplug before tampering
Don’t stick items in power outlets
Don’t overload circuits
•
•
•
•
Stay away from power lines
Don’t bypass safety features
Pull on the plug not the cord
Never remove the third prong (
•
Fuses & Breakers – devices that will
overloaded (example: too much current flowing)
)
a circuit if it becomes
[Read p 286]
Fuses:
• A device with a
than the wire it is connected to
• The metal strip melts
• This causes a
• A fuse
be
having a
melting point
the wire
in the
of electricity
Circuit Breakers
• Have a special
that
a
much electricity passes through
• The
produces
that causes the strip to
away from its contact point (Flips the breaker and breaks the circuit)
if too
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3 Prong Plug
•
3-prong plugs provide an
short
– 3rd prong is a
current away from the circuit
way for the electricity if there is a
 carries an
of
Recall that Lightening is:

Lightening Safety:
Your Task:
Check & Reflect p 287 # 1 - 10
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