Download File - Physical Science

Electric
Circuits
(continued)
Electric Circuits
• There are 3 parts to any
Electric Circuit:
1. Energy Source
2. Energy Conductor
3. Energy Receiver
Energy Source
Energy Receiver(resistance)
Energy Conductor
In order to work properly, electricity has to get :
1.To the device
2.Through the device
3.And back to the other side of the battery(or outlet)
Open Switch
•Electricity can’t move
through.
•Device will not work
properly!!
•Called an Open Circuit!!
Closed Switch
•Electricity can move through.
•Device will work properly.
•Called a Closed Circuit!!
Before you move
on, remember a
couple of things:
1. Voltage
determines
whether
electricity flows
or not!!
2. Resistance
determines
how much!!
Discuss the
dimmer switch
they forgot to use
in that Hotel!!
2 Types of Electric Circuits:
Series Circuit
Parallel Circuit
• Current has only one path
to take.
• All of the current will travel
through each device.
• “Cheap” Christmas tree
lights.
• Current has more than one
path to take.
• All of the current will not
travel through each device.
• “Expensive” Christmas tree
lights.
Series Circuit:
In a series circuit, if one
of the lights goes out,
what happens to the
remaining light(s)?
Hence, the
“Cheap
lights”!
Parallel Circuit
In a parallel circuit,
if one light goes
out, what happens
to the remaining
lights?
Hence, the
“Expensive lights!!
Remember this:
Because Stone Cold
Said So!!!
What determines whether
electricity will or will not
flow?
Voltage
What determines how
much electricity flows?
Resistance
Voltage in Series
There are 3 different
places that the river
in this picture
“drops”.
Voltage is highest at V1!!
It gets there first!!!
If you want to know
the total “drop” in
the river, you simply
add up the separate
“drops”!!
Same with Electricity!!!!
They do drop the
same amount!!
12 V
Loses 4 V
Loses 4 V
The Voltage drops
some as it passes
through each resistor!!
Loses 4 V
Each light will lose the same
Voltage and if each has the
same resistance, they will
each light up with the same
brightness!!
But what happens if
you add more
lightbulbs?
As you continue to add
lights, they will get dimmer
and dimmer!!
WHY???????
Why do lights get dimmer as you add
more of them to a series circuit?
• As you add more light bulbs, the resistance
gets bigger and bigger!!
• As resistance gets bigger and bigger, current
gets smaller and smaller.
• Remember, less current= less brightness!!!
Voltage in Parallel
This river has 3
different branches!!
They all follow
different paths, but
when they join back
together, how much
has each of them
“dropped”?
The Same Amount
Same with electricity!!!
Total Voltage
12 V
Therefore, the voltage along
any of the paths is 12 V.
If the light bulbs all have the
same resistance, the Current
through each will be the
same!!
Each light will “light up” with
the same brightness!
What if you add more bulbs?
1 Bulb
Notice the brightness!
2 Bulbs
Notice the brightness!
3 Bulbs
Notice the brightness!
4 Bulbs
Notice the brightness!
Because each branch of a
parallel circuit has the
same voltage, if the light
bulbs have the same
resistance, the same
amount of current will
flow through each.
They will always be the
same brightness!!
WHY???
Why do lights NOT get dimmer as you
add more of them to a parallel circuit?
• As you add more light bulbs, the resistance
actually gets smaller and smaller.
• As resistance gets smaller and smaller, current
gets larger and larger. There’s more of it.
• Enough to go to that other path without
changing the brightness!!
A
B
C
A
B
C
A
B
C
Series vs. Parallel Circuits
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Electric Charge and Circuits
lesson.