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Electricity
What is Electricity?
What is Electricity?
•Electricity is a basic part of nature and it is =
one =
of our
most widely used forms of energy.
•Electricity is measured in watts. One w=
att
is a very small amount of power.
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<=
span
style=3D'visibility:hidden'>•
How Is Electricity Generated?
•An electric generator is a device for converting <=
/span> mechanical energy into electrical energy. It is ba=
sed =
on the relationship between magnetism and <=
/span>=
electricity. When a wire or any other electrically=
conductive material moves across a magnetic field,=
=
an electric current occurs in the wire.
=
•Electricity is a by-product of other energy source=
s like coal, fossil fuels, and nuclear power.
Ele=
ctricity
Production By Source
![=3Duntitled](3D"slide0006_image002.gif")
Electric Current
•When the balancing force between protons =
and
electrons is upset by an outside force, an atom may gain or lose an
electron. When electrons are lost from an atom, the free movement
of these electrons constitutes an electric current.
=
•The stren=
gth or
rate of movement of the electricity is measured in amperes.&#=
13;
<=
span
style=3D'visibility:hidden'>•
Electrical Resistance
•Elect=
rical
resistance of an object is a measure of its opposition to the
passage of an electric current. It is measured in ohms. The
symbol for ohms is Ω.=
•To f=
ind
resistance, you use the formula R=3DV/I
•I=3Dthe current thro=
ugh
the object
•V=3Dpotential differe=
nce
across the object
•R=3Dresista=
nce of
the object
A 30-V
battery maintains current through a 10 ohm resistance. What is the current?=
•Use the formula R=3DV/I to solve. You need to <=
/span>m=
anipulate
the formula to use it. You are looking for I so you need to
change it to I=3DV/R
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•V=3D 30 V
(volts)
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•R=3D 10 <=
span
lang=3DEL style=3D'font-family:Arial;mso-ascii-font-family:Calibri;mso-bid=
i-font-family:
Arial'>Ω (ohms)
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•I=3D30/10=
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•Answer: 3=
A
(amperes)
Series Circuits
What is a Series Circuit?
•A series circuit is a
circuit in which all the lights are connected. If one light bu=
rns
out or a short in the circuit occurs, then the circuit will
be broken.
•An
example of a series circuit is a strand of Christmas lights.
<=
span
style=3D'visibility:hidden'>•
Four
15- Ω resistors are connected in series with a <=
/span>45-V battery. What is the current in the circuit?<=
/span>
![](3D"slide0012_image004.gif")
![3Dballs.png](3D"slide0013_image006.gif")
The slashes with 9V next to them is the <=
span
style=3D'font-size:156%'>battery. The plus sign is <=
span
style=3D'font-size:156%'>the positive and the <=
span
style=3D'font-size:156%'>minus sign is negative <=
span
style=3D'font-size:156%'>sides of the battery. The squiggles with the <=
span
style=3D'font-size:156%'>3k Ω is=
the
resister. This example is an=
<=
span
style=3D'font-size:156%'>example of a series circuit.
How does a Series Circuit Work?
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•A series circuit has=
more
than one resistor and gets its name from only having one pa=
th
for charges to move along. Charges must move in a
series going to one resistor then the next. If one of the items =
in
the circuit is broken then no charge will move through the circu=
it =
because
there is only one path.
How to build a Series Circuit?
How
Voltage Drops in a Series Circuit?
•The more lights you =
add to
a series circuit the dimmer the lights will get.
=
•Why? This=
is the
cause of to many volts being pulled off a battery.
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•V2 =3D IR2 =3D (V/R1 + R2)
∙ R2 =3D VR2/R1 +R2<=
/span>
Series Circuits
What is a Series Circuit?
•A series circuit is a
circuit in which all the lights are connected. If one light bu=
rns
out or a short in the circuit occurs, then the circuit will
be broken.
•An
example of a series circuit is a strand of Christmas lights.
<=
span
style=3D'visibility:hidden'>•
Four
15- Ω resistors are connected in series with a <=
/span>45-V battery. What is the current in the circuit?<=
/span>
![](3D"slide0020_image007.gif")
![3Dballs.png](3D"slide0021_image008.gif")
The slashes with 9V next to them is the <=
span
style=3D'font-size:156%'>battery. The plus sign is <=
span
style=3D'font-size:156%'>the positive and the <=
span
style=3D'font-size:156%'>minus sign is negative <=
span
style=3D'font-size:156%'>sides of the battery. The squiggles with the <=
span
style=3D'font-size:156%'>3k Ω is=
the
resister. This example is an=
<=
span
style=3D'font-size:156%'>example of a series circuit.
How does a Series Circuit Work?
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•A series circuit has=
more
than one resistor and gets its name from only having one pa=
th
for charges to move along. Charges must move in a
series going to one resistor then the next. If one of the items =
in
the circuit is broken then no charge will move through the circu=
it =
because
there is only one path.
How to build a Series Circuit?
How
Voltage Drops in a Series Circuit?
•The more lights you =
add to
a series circuit the dimmer the lights will get.
=
•Why? This=
is the
cause of to many volts being pulled off a battery.
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•V2 =3D IR2 =3D (V/R1 + R2)
∙ R2 =3D VR2/R1 +R2<=
/span>
Parallel Circuits
What is a Parallel Circuit?
•A parallel circui=
t
has more than one resistor (anything that uses electricity to=
do
work) and gets its name from having multiple (parallel<=
/b>)
paths to move along . Charges can move through
any of several paths. If one of the items in the circuit is brok=
en
then no charge will move through that path, but other paths will
continue to have charges flow through them.
What does it look like?
![3Dparallel.gif](3D"slide0027_image009.gif")
Find equivalent resistance
•Start by noting that=
the
total current in the circuit is the sum of thee currents
thought the branches of the circuit. Recall also that the potential
across each is the same. If I is the total current, and I1, I2,=
and I3 are the currents though each of the
branches, then I=3DI1 + I2 + I3=
Find equivalent resistance
•The current thou=
gh
each resistor, for example R1<=
span
style=3D'font-size:94%'>, can
be found from I1 =3D V/R1. The total current =
thought the equivalent resistance. R, of the =
circuit is given by I=3DV/R, but all potential dro=
ps in =
a parallel circuit are the same.
• V/R =3D V/R1 + V/R2 =3D V/R3
•Dividing both si=
des of
the equation by V then gives
and equation for the equivalent resistance =
of three parallel resistors,
•1/R =3D 1/R1 + 1/R2 + 1/R3
Total
Resistance and Current in a Parallel
Circuit
•Three resistors of 6=
0.0
Ohms, 30.0 Ohms. And 20.0 Ohms are connected in parallel
across a 90.0-V difference in potential
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•Find the =
current
in the entire circuit.
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•I =3D V/R=
=3D 90.0 V/
10.0 Ohm =3D 9.00 A
Total
Resistance and Current in a Parallel
Circuit
•Three resistors of 6=
0.0
Ohms, 30.0 Ohms. And 20.0 Ohms are connected in parallel
across a 90.0-V difference in potential
• 1/R =3D 1=
/60.0 Ohm
+ 1/30 Ohm + 1/20.0 Ohm
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•1/R =3D 6=
/60.0
Ohm
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•R =3D 10.=
0 Ohm
<=
span
style=3D'visibility:hidden'>•
Total
Resistance and Current in a Parallel
Circuit
•Three resistors of 6=
0.0
Ohms, 30.0 Ohms. And 20.0 Ohms are connected in parallel
across a 90.0-V difference in potential
=
•The volta=
ge drop
across each resistor is 90.0 V.
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•The curre=
nts are:
<=
span
class=3DBB style=3D'position:absolute;left:-3.92%'>•(for R1) I1 =
=3D V/R1 =3D 90.0 V/60.0 Ohm =3D 1.50 A
<=
span
class=3DBB style=3D'position:absolute;left:-3.92%'>•(for R2) I2 =
=3D V/R2 =3D 90.0 V/30.0 Ohm =3D 3.00 A
<=
span
class=3DBB style=3D'position:absolute;left:-3.92%'>•(for R3) I3 =
=3D V/R3 =3D 90.0 V/20.0 Ohm =3D 4.50 A
<=
span
style=3D'visibility:hidden'>•
Presented by:
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•Trey Smith
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•Tyson Min=
or
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•Ian Soper=
<=
span
class=3DBB style=3D'position:absolute;left:-4.43%'>•Tyler Par=
rish
' + ENDSHOW_MESG + '
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tes![](3D"buttons.gif")
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