Transcript Electricity - thorntonso

Electricity
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ELECTRICITY comes from the electrons in an atom.
Electrons
Negative Charge
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Electricity
Static Electricity
Build-up of electrical charge
Electrical Current
Flow of electricity through wires
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Electricity exists naturally in nature…
Static Electricity
For example:
Lightning
Zap!
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Electric Charge
The source of static in lightning and shocks
is electric charge.
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Most objects tend to be
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Net Charge of Objects:
Neutral Object
Charged Object
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-6
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Net Charge:
0
+10
Net Charge:
+4
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Opposites Attract
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Same Charges Repel
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How do balloons stick to
walls?
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1. Rub a balloon on a
sweater to “charge it up.”
2. Negative charges in
the wall repel from the
balloon.
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3. The balloon sticks
because the positive
charges left over are
attracted to the balloon.
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The Electroscope
Metal rod
Electricity can
move down the
metal rod to
the two gold
leaves.
2 Gold “leaves”
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The Electroscope
When a rubber comb with a build-up
of static electricity is touched to the
rod...
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…the electric charge travels
down the rod AND...
...builds up on both
sides of the gold strip.
Since the charge of the
leaves are both
negative the two sides
of the strip repel one
another.
- -
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A battery uses chemical
energy to move electrical
charges.
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Circuits flow
in a circular path
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Measurement of energy
IF = 1.5 volts
?V
3.0V
1.5V
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Voltage
The unit for voltage is volts (V)
and is a measure of “potential difference.”
Potential Energy
(height)
1.5 V
Potential Difference
1.5 Meters
0.0 V
To Lower Energy
The potential difference
(voltage) is 1.5 V.
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Voltage
The higher the energy, the greater the voltage
(potential difference).
3.0 V
Higher Potential
energy (height)
Greater
Potential Difference
3.0 Meters
0.0 V
To Lower Energy
The potential difference
(voltage) is 3.0 V.
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Current
is the rate of the flow of an
electrical charge.
How fast (speed) is
the electricity flowing
through these wires?
The rate that the electricity flows is called CURRENT
CURRENT is measured in AMPS (I).
How fast is this water coming out?
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TYPES of CURRENT
Direct Current (DC)
flows in one direction.
Alternating Current (AC)
flows back and forth.
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RESISTANCE
Which of the pipes below would allow water out faster?
The smaller pipe would have more resistance to the flow.
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Resistance is measured in ohms.

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to Electrical Current
Which of the following do you think would be
most resistant to electrical current?
Plastic
Glas
s
Rubber
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These materials allow electrical charge (current) to
move easily through them. They have little resistance to
the flow of electrical current. They are
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Glass
Plastic
Rubber
These materials do not allow electrical charges
(current) to move easily through them. They have a
strong resistance to the flow of electrical current.
They are
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Conductors and Insulators:
• Conductors allow charges to flow easily.
– Examples include copper, silver, and aluminum.
• Insulators do not allow charges to flow easily
– Examples include glass, plastic, and rubber
Rubber insulation
Copper
Wire
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Wires carry an electrical charge.
Copper wire covered in rubber insulation
The “human” wiring system:
The neuron (nerve cell)
Insulation
(Myelin Sheath,
fatty tissue)
Wires (nerve fibers)
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Match the word on the left to the phrase on the right.
Resistance
Ohms
How Fast?
 or R
Current
How much?
AMPS (I)
Voltage
Volts (V)
How much is it slowed
down?
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We can use this formula to figure out
volts, current (amps) and resistance.
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Calculate the potential difference (volts)
across a 3  resistor if a 0.5 A current is
flowing through it.
V=Ix
What do you know?
V=?
I = 0.5 A
V = 0.5 A x 3 
1.5 V = V
=3
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A radio with a resistance of 240  is
plugged into a 120 V outlet. What is the
current flowing from the outlet?
V=Ix
What do you know?
V = 120 V
I= ?
 = 240 
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120 V = I x 240 
240 
240 
0.5 amps = I
or V/ 
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