Download File - Ms. Lokseth`s Classroom

Ms. Bodnar
Chapter Two
Chapter Two: Technologies Can Be Used to Transfer and
Control Electrical Energy
2.1 Controlling the Flow of Electrical Current
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Neon Lights as a Circuit:
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Electricity must travel all the way through the tube to make neon gas glow
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Sign must be equipped with on/off switch
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Must be contained so no accidental electrocution
A Unique Circuit
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These neon lights are tubes filled with different types of gases (gas is the conductor),
metal terminals are on either end of the tube; thereby, ____________________________
_________________________________.
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Neon gas is an insulator by when current is applied atoms get excited and they free
themselves from the atom
Conductors and Insulators
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Insulators- electrons are tightly bound to the nucleus = less likely to break away
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Conductors- electrons loosely bound to nucleus = more likely to break away
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When you apply a voltage, ____________________________________________
__________________________________________________________________
__________________________________________________________________
Unit D: Electricity
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Ms. Bodnar
Chapter Two
Superconductors
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___________________________________________- perfect conductors, they have no
resistance to electron flow
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Discovered by Heike Kamerlingh Onnes
▫
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At - 273oC, mercury is a superconductor
___________________________- allows electric current to pass, but provides resistance
to it (limits the amount of current going through)
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_____________________________- measure of how difficult it is for electrons to flow
through a substance
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____________________________- the measure of resistance (Ω)
Solutions as Resistors
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Solutions can conduct electricity as long as they have a conducting solute
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Minerals in water gives water the ability to conduct electricity
Polygraph Machine
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Measures skin resistance, blood pressure, and respiration
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When lying those factors will cause a spike on the computer screen due to an increase in
resistance
How do Switches Work?
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When the switch is on the two conductors are pressed together thereby completing the
circuit
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When the witch is off the two conductors aren’t touching = no circuit
Doorbell
Unit D: Electricity
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Ms. Bodnar
Chapter Two
Variable Resistor or Reostat
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____________________________- resistor whose resistance can be changed by
adjusting the portion of the resistor the current travels through
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This will increase or decrease the amount of current in the circuit by adjusting the portion
of the resistor that current travels through.
Check and Reflect:
Page 303 #1-10
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Ms. Bodnar
Chapter Two
2.2 Modeling and Measuring Electricity
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Electricity needs a source if it is going to supply energy to different places. The stronger
that source is, the stronger the electricity is going to be.
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Electricity will not flow without a difference in electrical potential (will flow from high
to low)
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Higher voltage coming from power station will have more electrical potential energy
Resistance and Current
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Current ___________________________________________________________ in a
circuit (smaller pipe = less flow)
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Interrupt the path = more resistance = less current
Unit D: Electricity
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Ms. Bodnar
Chapter Two
Ohm’s Law
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States that as long as temperature stays the same:
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_________________________________________________________________
▫
_________________________________________________________________
(current = voltage)
Using Ohm’s Law
Examples:
A 30 V battery creates a current through a 15 Ω resistor. How much current is created?
Unit D: Electricity
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Ms. Bodnar
Chapter Two
A motor has an internal resistance of 40 Ω. The motor is in a circuit with a current of 4.0 A.
What is the voltage?
A current of 625 mA runs through a bulb that is connected to 120 V. What is the resistance of the
bulb?
Unit D: Electricity
Science 9
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Ms. Bodnar
Chapter Two
Using Test Meters
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_____________________________– instruments for measuring potential difference in
volts
•
•
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Voltage Drop- potential difference across a resistor or device
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Millivoltmeters- used to measure small voltages
_____________________- used to measure electrical currents in amperes
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How many electrons pass through the circuit each second.
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Galvanometers- meters used to measure small currents
_______________________________- you can measure any of the variables: voltage,
current, or resistance.
▫
Make sure you select the right variable
Types of Resistors
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Depends on how much voltage goes through them
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____________________________________: wire made of heat-resistance alloy wrapped
around an insulating core (0.1 Ω to 200 Ω)
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____________________________________: made of carbon mixed with other materials.
Cheaper to make but less precise (10 Ω to 20 Ω)
Check and Reflect:
Page 310 #1-10
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Ms. Bodnar
Chapter Two
2.3 Analyzing and Building Electric Circuits
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_________________________________- there are special symbols that are for certain
parts of a circuit.
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_________________________________- drawing made with special circuit symbols.
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Parts of a circuit:
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________________________________ (energy and electron supply),
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________________________________ (path for current),
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________________________________ (controls current flow),
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________________________________ (converts to another form of electricity)
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Ms. Bodnar
Chapter Two
Circuit Analysis: Bulldozer
Series Circuit
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Series circuit- ____________________________________________________________
________________________________________________________________________
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One path...if interrupted, no flow
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More light bulbs = more resistance = decrease current = dimmer lights
Parallel Circuit
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Parallel circuits- __________________________________________________________
________________________________________________________________________
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Interruption in one path will not affect the other
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This means that there is little resistance therefore all light bulbs will remain the
same intensity
Unit D: Electricity
Science 9
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Ms. Bodnar
Chapter Two
Applications of Series and Parallel Circuits
1. __________________________________________- use parallel circuits. Why?
2. ______________________________________________- circuit made up of
miniaturized components, especially an integrated circuit (circuit of inseparable, often
microscopic, components formed on the surface of a single piece or chip of
semiconductor crystal, usually silicon)
a. ____________________________________- solid-state components because
they are made of solid material with no moving parts...three layers of silicon
(middle layer acts as a switch)
Check and Reflect:
Page 316 #1-11
Page 317 #1-9
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