Two circuit handouts
Two circuit handouts
Two circuit handouts
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Period: I Circuits and Symbols [<br />
Ch. 6:2<br />
Electricity works a lot like<br />
water. Often knagining how<br />
water would work in an<br />
ckcuit wilt tell you how<br />
electricity will work as well.<br />
Electricity flows through <strong>circuit</strong>s: paths of conductors (usually wires),<br />
Any break in the <strong>circuit</strong> will cause the <strong>circuit</strong> to fail, just like a break in<br />
a pipe lets water leak out of a water system.<br />
A closed<br />
<strong>circuit</strong> has<br />
no breaks:<br />
the light<br />
lights up.<br />
An open<br />
<strong>circuit</strong> has a<br />
break in it:<br />
the light<br />
will not<br />
light up.<br />
A break in a <strong>circuit</strong><br />
is any spot where<br />
an insulator is in<br />
the way of the<br />
electricity’ s flow.<br />
Paper, plastic, or<br />
even an air gap<br />
can keep electricity<br />
from flowing~<br />
I<br />
Circuit diagrams are a short-cut method of drawing<br />
<strong>circuit</strong>s. They don’t need to be perfectly draw,<br />
but they can be drawn wrong.<br />
Circuit diagrams<br />
Electrical Symbols<br />
bakery<br />
[ capacitor<br />
These components look similar, but are<br />
very different and have different functions.<br />
wire<br />
battery<br />
-T-<br />
~aths for electricity<br />
to flow.<br />
pushes electricity<br />
through <strong>circuit</strong>.<br />
pipes<br />
pump<br />
light bulb<br />
light bulb<br />
lights up; resists<br />
electricity.<br />
equivalent<br />
switch<br />
switch<br />
turns electricity<br />
on and off<br />
valve<br />
The diagram on the right is a faster way of<br />
drawing the <strong>circuit</strong> on the lefk (Notice the<br />
direction of the battery, which is important)<br />
resistor<br />
resists flow of<br />
electricityl<br />
restriction<br />
in a pipe<br />
Voltage Pushes Electrons<br />
The ends of a battery<br />
are oppositely<br />
charged. This<br />
creates a force,<br />
pushing electrons<br />
thrOagh the <strong>circuit</strong>.<br />
3 Quantities of a Circuit<br />
The flow of electrons we call current<br />
which travels through closed <strong>circuit</strong>s,<br />
Resistance Resists Current Flow [<br />
Devices in the <strong>circuit</strong> do work, which<br />
slows down (restricts) current.<br />
Circuit<br />
continues<br />
Voltage is measured in Volts. Current is measured in Amps. Resistance is measured in Ohms.<br />
www.aisd.net/smurray<br />
These three quantities are lk~ed in any <strong>circuit</strong>.<br />
Change one of them and one or both of the others will change.<br />
Copyright © 2004, C. Stephen Murray
Period:<br />
Types of Circuits and Ohm’s Law<br />
Ch.7:1<br />
Series <strong>circuit</strong>s have all only one<br />
path for the electricity to flow.<br />
<strong>Two</strong> lightbulbs in series,<br />
Each light is dependent<br />
on the other.<br />
If any part of a series<br />
<strong>circuit</strong> is broken, the<br />
<strong>circuit</strong> fails. If either<br />
light is unscrewed both<br />
lights will turn off.<br />
The branches (paths)<br />
of a parallel <strong>circuit</strong> are<br />
independent. If either<br />
light is unscrewed, the<br />
other will remain on.<br />
Your house is wired in parallel, so that each light and<br />
appliance can be turned on and off independently.<br />
Parallel <strong>circuit</strong>s have multiple<br />
paths for the electricity to flow.<br />
<strong>Two</strong> lightbulbs in parallel.<br />
Each light is independent<br />
of each other.<br />
Ohm’s Law I<br />
Voltage<br />
V ~ (in volts)<br />
Current ~ | __~<br />
(in amps)-- ~" --<br />
R ..~._._ Resistance<br />
(in ohms)<br />
Current equals the voltage<br />
divided by the resistance.<br />
Also, V = IR and R = V/I<br />
Abbreviations:<br />
A - Amps - current<br />
v - volts - voltage<br />
~ - ohms - resistance<br />
Increasing voltage<br />
increases current<br />
Increasing resistance<br />
decreases current,<br />
Decreasing voltage<br />
decreases current<br />
Decreasing resistance<br />
increases current.<br />
Ex. How much current does a 12 v<br />
battery push through a 3 ~ resistor<br />
V = 12v<br />
~_=3~<br />
I=<br />
I=V = 12v @<br />
R 3~<br />
Ex. How strong a batteryproduces<br />
2 A through a 3 D resistor<br />
V=v i=~<br />
V So, V= IR<br />
R=3D R = (2A)(3a)<br />
I=2A<br />
Current<br />
Voltage<br />
J<br />
I Resistance I<br />
Current is moving electrons,<br />
moving charge.<br />
Increasing current causes<br />
more electricity to move<br />
through a device.<br />
Increasing electricity through<br />
a device causes it to work<br />
faster (in a motor) or be<br />
brighter (in a lighthulb).<br />
www, aisd net/smurray<br />
Using Otma’s<br />
Law: I = V/R<br />
Using Ohm’s<br />
Law:I = V/R<br />
More current =<br />
brighter light.<br />
Voltage is electrical potential:<br />
how much work a battery can do.<br />
Voltage is linked to energy:<br />
I volt of voltage = 1joule of energy<br />
per coulomb of charge<br />
To increase voltage you could use a<br />
stronger battery OR add batteries.<br />
~<br />
1.Sv~<br />
9volts 1.5 v U 3 volts<br />
total<br />
More voltage is like a<br />
stronger pump, giving more<br />
force and more current.<br />
0 volts total<br />
The lightbulb doesn’t<br />
light here, because<br />
the two batteries are<br />
pushing opposite<br />
directions. To add<br />
together, batteries<br />
must be facing the<br />
same direction.<br />
Resistance slows down current.<br />
Third( of resistance like<br />
a dam holding back water.<br />
Adding devices in a <strong>circuit</strong><br />
increases resistance.<br />
I = V/R<br />
= 6v/3~ = 2 A<br />
The light is bright<br />
because the 6<br />
volts only have<br />
one light to ran.<br />
I = V/R<br />
~<br />
_~_x~ = 6v/6~ = 1 A<br />
Both lights are<br />
dimmer because<br />
the 6 volts have<br />
two lights to run.<br />
More resistance = less current<br />
Less current = less fight<br />
Copyright © 2004, C. Stephen Murray