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IPS: Unit 2.5 “I Just Couldn’t Resist Lighting Up Again”
name _____________________
WHAT DO YOU THINK?

What affects the amount of current passing through a circuit?
a. __________________________________
b. __________________________________
c. __________________________________
d. __________________________________

How can you dim a light bulb? __________________________________________________________
___________________________________________________________________________________
FOR YOU TO DO.
1. Wire the circuit pictured in the schematic at the right.
Your teacher will give you a long piece of copper
wire about one meter long. Measure the current
passing through the circuit, the voltage gain of the
battery, and the voltage loss of the bulb and the long
copper wire.
Current passing through the circuit: I = __________
Voltage gain of the battery VS = ____________
Voltage loss of the light bulb: VB = __________
Voltage loss of the copper wire: VCW = ___________
2. Wire the circuit pictured in the schematic at the right.
Your teacher will give you a long piece of nichrome
wire to replace the copper wire used in #1. Make sure
you spread out the wire so it does not touch itself.
Measure the values shown.
Current passing through the circuit: I = _____________
Voltage gain of the battery: VS = ____________
Voltage loss of the light bulb: VB = __________
Voltage loss of the nichrome wire: VNW = __________
IPS: Unit 3.5
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3. What happened to the current passing through the circuit in #2 compared to #1?
4. What happened to the voltage drop across the nichrome wire as compared to voltage drop across the
copper wire?
5. What happened to the brightness of the bulb when the nichrome wire was used?
6. Which wire is a better conductor of electricity, the nichrome wire or copper wire? Think about this a
little before you answer.
7. Which wire has more resistance?
8. What do we mean by resistance?
9. What is the unit for resistance
10.
What is the schematic symbol for a resistor? ____________________________
11.
Complete the following table.
A. Start with the circuit that you already wired with the
long nichrome wire.
B. Loosen the screw on the meter and shorten the
nichrome wire so that it is one half its original length.
C. Shorten the nichrome wire so that it is one quarter of
its original length.
D. Shorten the nichrome wire so that it is one eighth of
its original length.
12.
Length of
wire
Current - I
amps
Brightness of
bulb
Full
1/2
1/4
1/8
How does a dimmer switch work?
13. Now try a thin nichrome wire. How does it compare to the copper wire and thicker nichrome wire?
__________________________________________________________________________________
13. Take out the nichrome wire from your circuit and insert a dimmer
switch to complete the circuit. Turn the knob on the dimmer
switch and see what happens to the light bulb.
14.
What is a rheostat (dimmer switch)?
15.
a) What is the schematic symbol for a rheostat?
b) Draw a schematic of a circuit with a battery, light bulb
and a rheostat (dimmer switch).
IPS: Unit 3.5
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PHYSICS TO GO.
Ohm's Law Problems
What is the equation for Ohm's Law?
Write the equation in the memory circle at the right.
Show the equation and your work to solve the following
problems.
1.
When a given light bulb is connected to the 120-volt outlet of a house a current of 0.4 amps passes
through it. What is the resistance of the bulb?
2. When another, brighter bulb is also connected to the 120 volt outlet of a house a current of 1 amp passes
through it. What is the resistance of this bulb?
3. When a toaster is plugged into the 120 volt of a house a current of 10 amps passes through it. What is
the resistance of the toaster?
4. A hair dryer has a resistance of 8 ohms. How much current will pass through it when it is plugged into a
120-volt outlet?
5. What properties of a wire affect its resistance? How does each property affect the resistance?
IPS: Unit 3.5
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