Download Chapters 20 and 21: Electricity

Know the cause and effect of
static electrical charges
PA Anchor: S8.C.2.1
• Like charges repel
+
+
--
or
• Opposite charges attract
--
+
--
• Buildup of charge on an object creates static electricity
• Charges do not flow
• Static discharge – loss of static electricity as electrons move until
both objects have the same charge
• Lightning
• Walk across carpet
• Van de Graaff
Generator
Apply concepts of voltage,
current, and resistance
PA Anchor: S8.C.2.1
• The amount of charge that flows each second
• Units: Amperes (A)
• This is often shortened to “amps”
• Another common way to express current is in milliamps
(1000 mA = 1 A)
• Electrical Potential
• Potential energy per unit of charge
• Voltage / Potential Difference
• Difference in electrical potential
• Units: Volt (V)
• Voltage Source
• Ex: Battery, Outlet, Generators
• Resistance
• Opposition to flow of charges
• Units: Ohms
• Symbol: Omega ()
1.
Voltage Source

2.
Conductor

3.
Battery
Metal wire
Closed Path / Loop

No holes / breaks
V= I R
Voltage = Current  Resistance
Voltage = Energy
Current = Charge
Resistance = Opposition to Flow of Charge
V = IR
Symbol:
Unit:
V
Volt (V)
Current
I
Amps (A)
Milliamps (mA)
Resistance
R
Ohms ()
Voltage
• An automobile headlight is connected to a 12 V battery. If the
current is 0.40 A, find the resistance of the light.
• Find the voltage needed to run a waffle iron if the current
required is 12 A and the resistance is 10 .
Identify circuit symbols on an
electrical circuit diagram
PA Anchor: S8.C.2.1
Name
Symbol
Battery
Resistor
Switch
Ground
Bulb
Open
Closed
Distinguish between series and
parallel circuits
Describe different arrangements of
cells, resistors, lamps, and switches
in an electrical circuit
PA Anchor: S8.C.2.1
• Only one path for
current to flow
Draw this one:
Don’t draw this one:
• Multiple paths for current to flow
Draw this one:
Don’t draw this one:
• Series
• Advantages:
• Simple to build / design
• Disadvantages:
• One bulb out = all out
• Bulbs dim as you add them
• Parallel
• Advantages:
• One bulb out = others stay
lit
• Brightness doesn’t change if
you add bulbs
• Disadvantages:
• More complex to build
Compare and contrast direct
and alternating current
PA Anchor: S8.C.2.1
• Direct Current (DC)
• Current flows in only one direction
• Ex: Batteries (12 V, 9 V, 1.5 V)
• Alternating Current (AC)
• Current flows back and forth
• Ex: Outlets (120 V)
Define and compare digital
and analog signals
PA Anchor: S8.A.3.2
S8.A.3.3
• The use of electricity to control, communicate, and process
information
• Based on electronic signals
• Electronic signal – a varying electric current that represents
information
• Analog – current is
varied smoothly to
represent information
• Digital – current changes
in steps
• Ex: Playing a record
• Ex: Playing a CD
Describe the use of
semiconductors in electronics
PA Anchor: S8.A.3.2
S8.A.3.3
• We already talked about conductors and insulators…what
about semiconductors?
• Definition: a material that conducts current better than
insulators, but not as well as conductors
• Diode – allows current to flow in only one direction
• Transistor – amplifies electronic signal or switches current on or
off
• Integrated Circuit – a circuit manufactured on a tiny piece of
semiconductor (chip)
Explain how telephones, televisions, and
radios transmit and receive signals.
Explain the difference between AM
and FM radio signals
PA Anchor: S8.A.3.2
S8.A.3.3
• EM Waves allow for electronic signals to be carried over long
distances
• Transmitter –converts sound into an electronic signal
• Receiver – converts electronic signal back to sound
• AM Radio
• FM Radio
• AM = Amplitude
Modulation
• FM = Frequency
Modulation
• The amplitude of the
wave is changed
• The frequency of the
wave is changed