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Electricity
Electrical
Force
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• An object becomes charged by
– Friction
– Conduction
– Induction
Charging
by Friction
Charging by induction.
Charging by conduction.
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Potential
Electricity can be
described like
flowing water.
Current
Load
Charge flows
in an Electric
Circuit.
Switch
Charge is a quantity of electricity.
Charge has the unit coulomb (C).
An electric circuit has 4 parts:
Switch
Load
Power
Source
Connecting Wires
Flowing charge is called current. The
symbol is I and the unit is the ampere or
amp (A).
SIM
– Voltage is a measure of the potential difference
between two places in a circuit.
– The unit is the Volt (V).
– Voltage IS Potential Energy!!!
– Voltage IS NOT flowing charge.
Batteries convert
chemical energy into
electrical energy!
douglasbattery.com
1. Dry Cell Battery
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2. Wet Cell Battery
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Power plants use
generators to
produce power.
This generator is
called a turbine.
AC/DC
•Direct current (DC) is charge moving in one direction
•Alternating current (AC) is charge moving back and
forth.
•Batteries produce direct current (DC).
•The power company uses electrical generators to
produce alternating current (AC).
•120V of AC is available at your house’s wall sockets.
•It is more efficient for power companies to send AC to
your house, but most electrical devices need DC.
•These devices have components inside them that
convert AC into DC.
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120V AC
9V DC
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1.5V DC
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Electrical Resistance.
– This is when current flow is slowed down.
– Current seems to lose energy. Actually, the electrical
energy is converted into heat and/or light.
– The symbol is R.
– The unit is the ohm ().
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Water Heater Element
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Stove Top Burners
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Light bulb
A conductor’s electrical resistance depends on Four
Variables.
• The length of the conductor.
• The cross-sectional area of the conductor.
• The material of which the conductor is made.
• The temperature of the conductor.
The relationship between voltage, current, and
resistance is
V = I · R or Ohm’s Law
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V = Voltage
I = Current
R = Resistance
(SIM1) (SIM2)
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Digital Multimeters
can measure voltage,
current, resistance,
and more.
Electrical Work.
• A voltage source does work when releasing charge.
• The unit of electrical work is joules (J).
Electrical Power.
• The unit of power is called the watt (W).
• power = current · voltage
P=I ·V
Paying for Electricity.
• The electric company charges you based on the
amount of power and the amount of time.
• The unit is kilowatt-hour (kW-hr).
• 1 kW = 1,000 Watts
eere.energy.gov
Several
things in
our homes
consume
electricity.
eere.energy.gov
The hot
water heater
uses
electricity to
heat water.
Look for this
sticker to find
out how your
appliance
compares to
others that are
similar.
eere.energy.gov
Does it cost more to
use a 100-W light bulb
for 1 hour or 3 hours?
SIM
Does it cost more to
use a 100-W light bulb
for a 60-W light bulb?
This meter can usually be found outside our
home. It keeps track of the amount of electrical
power that your home uses over time.
It is illegal
to tamper
with it!!!
Where does electricity come from?
Electricity
is not
entirely
efficient.
Sources
• Bloomfield, How Things Work.
• Krauskopf & Beiser, The Physical Universe. 10th ed.
• Tillery, Physical Science.