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Investigation 2
Part 1
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This is a new component you will be
investigating today.
The schematic symbol for a resistor is
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Resistors are used in some circuits. Work with
your partner to find out what resistors do
when they are placed in a circuit along with
other components – battery, switch, lamps.
Getters – get your springboard bag and 1
resistor from each of the 4 cups.
Update your inventory card to include the 4
resistors.
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Some resistors conduct electricity and others do
not. (Actually, all resistors conduct electricity, but
not enough to light the lamp.)
All resistors in series with lamps make the lamp
grow dimmer.
Each different resistor in series with a lamp
makes it glow with a different brightness.
Some resistors in parallel with lamps make the
lamp dim a tiny bit; some resistors in parallel
with lamps don’t affect the brightness of the
lamps.
Some resistors get warm when they are in
parallel with a lamp.
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The resistors make the lamps dimmer. How
can you explain this observation.
What do you think is happening inside the
resistor to cause the lamp to burn with such
reduced intensity?
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Are these statements accurate?
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Resistors push back on electricity.
Resistors use up electricity.
Resistors slow down electricity.
Resistors clog up the circuit.
Electricity gets stuck in resistors.
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Read the sequence of colored bands on one
of the resistors starting at the end that is
NOT gold.
These color bands are the “names” of the
resistors. One resistor is named
orange/orange/brown. What are some of the
other names?
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Which resistor allowed the lamp to glow the
brightest?
◦ Violet/green/black
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Which resistor allowed the lamp to glow the
dimmest?
◦ Brown/black/red
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Put the resistors in order from brightest to
dimmest.
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Violet/green/black
Brown/green/brown
Orange/orange/brown
Brown/black/red
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Be sure to put your resistor investigation
records in a safe place – you will need them
for the next investigation.
Return and inventory all components to the
components bag.
Secure battery leads.
Return all materials to the table.
Part 2
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Were all four of your resistors the same?
How do you know they are different?
What is one way to tell resistors apart by
looking at them?
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Resistors are different from one another.
Some make lamps glow dimly. Others let
lamps glow brightly. Different resistors have
different amounts of resistance. Some
resistors have a lot of resistance while others
have very little resistance.
Resistance is measured in units called ohms.
The symbol for the ohm is the Greek letter
omega (Ω). For instance, a resistor with a
resistance of 100 ohms is written 100Ω.
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Which resistor has the greatest resistance?
Which resistor has the least resistance?
How do you know?
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What is a code?
The color bands on the resistors are a code
that tells the resistance of each resistor.
The resistance can be anywhere from 1 ohm
to several million ohms.
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Each of the 10 colors used
in the code represents a
different numeral from zero
to nine.
Read the code starting at
the end opposite the gold
band.
Band 1 is a number and
band 2 is a number, but
band 3 is the number of
zeros to add after the first
two numbers.
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Lab book – Resistor Investigation
Look at the 6 hypothetical resistors at the
bottom of the sheet.
Decode the resistors – 3 minutes
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Red/green/brown – 250 Ω
Grey/black/black – 80 Ω
Yellow/blue/green – 4,600,000 Ω
Black/orange/black – 3 Ω
Violet/black/red – 7000 Ω
Brown/red/orange – 12,000 Ω
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Decode the resistors in your
bags.
Write the ohm values on the
line beside the color codes
(3 minutes).
Answers:
◦ Violet/green/black – 75 Ω
◦ Brown/green/brown –
150 Ω
◦ Orange/orange/brown –
330 Ω
◦ Brown/black/red – 1000
Ω
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What is the relationship between the amount
of resistance in the circuit and the brightness
of the lamp?
Answer – there is an inverse relationship
between brightness and resistance in a series
circuit.
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Create a color code
card for identifying
resistors.
Keep it in you binder.
Part 3
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When scientists, engineers and technicians
who work with electricity need accurate
information about what is going on with a
circuit, they use a meter.
http://www.fossweb.com/modulesMS/kit_mu
ltimedia/Electronics/content/co_mu_in_274_
1.htm
They are precision
instruments and must
be handles with care.
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There can not be any electricity flowing
through a component when you are
measuring resistance. Resistance is measured
in components when they are NOT part of a
circuit. If electricity flows to the probes when
you are measuring resistance, the meter will
be damaged.
NEVER attempt to measure the resistance of a
battery – it will damage the meter.
Turn meters OFF before storing them at the
end of class.
Probe
Display Screen
Rotary Switch
Rotate the switch to
2000 Ω.
The number 1 in the
display indicates the
meter is ready to
measure resistance.
Touch the 2 probes
together at the tips.
The 0 indicates the
meter is reporting no
resistance.
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Review Resistor Accuracy – the gold band is
the manufacturer’s way of telling us the
resistor is no more than plus or minus 5% of
the claimed value.
100 Ω
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How could you test your resistors to see if
they are accurate?
Record your measured resistances on the
Resistor Investigation Sheet.
What is the resistance of a piece of wire?
Write down its band code.
What is the resistance of a lamp?
Write down its band code.
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Wire – black/black/black
Lamp – red/black/black
0Ω
20 Ω
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Compute the percentage of error for each of
the 4 resistors.
Add a fourth column to page 7 and record
your % error there.
Are they within the 5% acceptable range?
Part 4
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Has 2 wires that can be used to connect it in
a circuit with other components.
Your job is to figure out what it does in a
circuit.
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DO NOT connect the potentiometer to the
battery itself. Use it only in a series with other
components.
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The potentiometer can turn the light off or
make it very bright.
It can make the light dimmer or brighter.
It acts like a changeable resistor.
It is like a volume control for a light.
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The potentiometer is a resistor that can be
changed by turning the wheel.
They are used in a variety of situations.
◦ Light dimmers
◦ Volume controls on audio devices
◦ Speakers balance adjusters
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What do you think might be inside a
potentiometer that would produce the
variable resistance?
Why do you think you were cautioned not to
connect the potentiometer to the battery?
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What is the MOST resistance and the LEAST
resistance the potentiometer can impose on a
circuit?
REMEMBER to remove the potentiometer from
the circuit BEFORE testing its range.