Download Kreutter: Magnetism What is Magnetism? Part 1: A Magnet Take 2

Kreutter: Magnetism
What is Magnetism?
Part 1: A Magnet
1.
Take 2 magnets.
a. What do you notice about how they interact? Are there “rules”? If so, what are they?
b.
What other physics concept(s) do these magnetic rules remind you of? Why? Similarities?
Differences?
c.
Pay special attention to the broken magnet. What is interesting about the broken magnet compared
to the “whole” magnet?
d.
Is it possible to have a magnet that only has a North pole or one that has only a South pole?
Defend your answer.
e.
Is it possible to have an electrical charge that is only positive or only negative? Defend your
answer.
f.
Will a magnet interact with any other objects, or just other magnets?
g.
If a magnet is touching another object (say a nail) what happens to that object?
Use your answers to the above questions to come up with a model for what a magnet might look like on an atomic
level. Draw something that you are thinking about, even if you are not sure how a magnet “works”.
2.
Put some iron filings in a plastic dish (not too many; it only takes a little). DO NOT PUT THE MAGNET
IN THE DISH WITH THE FILINGS. Hold the magnet underneath the dish. Draw the pattern that you see
for one and 2 magnets.
Kreutter: Magnetism
3.
Move the compass around a magnet. Record your observations. (What happens to the compass needle as
you move the compass around the magnet? The easiest way to fully record this is to draw a picture.)
a.
How are these observations consistent with the observations you made in question #2?
b.
What can you infer about the compass needle?
c.
What can you infer about how magnets interact with each other and with other materials?
4.
Now, holding the compass, walk around the room. What are your observations? Considering your previous
observations, what, if anything, can you conclude about the compass needle? About the classroom?
5.
Make a simple circuit with a D battery and 2 wires. You should tape the battery and wires together. You
should include a light bulb so you are sure current is flowing. Be sure one of the wires in the circuit is
aligned along the geographical North-South direction (use the compass to determine this before you hook
up your circuit). Place the compass underneath the North-South wire before you hook up the battery.
Connect your circuit. Which way is the compass needle pointing? Record your observations.
6.
What, if anything, can you infer about the electric circuit? Be sure to observe the compass needle when the
circuit is “live” (there is current) and the circuit is “dead” (no current flowing).
Kreutter: Magnetism
7.
Change the polarity of the circuit (as simple as flipping the direction the battery is facing—negative to
positive). Observe the effects of the circuit on the compass again. Do you notice any differences? Which
way is the compass needle pointing? Record your observations here.
8.
Compare the behavior of the compass when it was exposed to a magnet to its behavior when it is exposed
to an electrical current. What can you conclude?
9.
Use the thumb of your right hand to represent the direction of the current and your four fingers of your
right hand to represent the direction of the compass needle. Does the orientation of your thumb and fingers
describe a pattern between the direction of the current and the orientation of the compass needle for all of
your experiments? Describe any patterns you notice.
10. Develop a model for why electric current (moving electrically charged particles) might affect the behavior
of magnets differently than stationary charged objects would.
11. Build the circuit shown below. The wire needs to be wrapped securely around the nail and your loops
should be even. This set-up tends to drain the battery very quickly, so unhook the apparatus as soon as you
have made your observations. Does your nail pick up paper clips? If so, you have made an electromagnet.
a.
b.
What variables can you manipulate that you think might affect the strength of the electromagnet?
What will be your dependent variable?
Kreutter: Magnetism
c.
Do the experiment. Change the variables that you can and assess that variable’s effect on your
dependent variable. Record your results.
Independent Variable Changed/How?
Dependent Variable Changed/How?
d.
Back to your magnet model—an electric current can turn a nail into a magnet. How does this
affect your model of what magnetism is?
Faraday lab
Part II: Recreate Faraday’s experiment with compasses and current carrying wire
1. Set up a series circuit:



Power source
One alligator clip segment of wire
Ammeter
2. DRAW YOUR CIRCUIT. Make sure current is flowing by checking the ammeter.
3. Disconnect one alligator clip and pass one section of wire through the center of a sheet of paper.
4. Reconnect the clip and turn the power on so current flows. Set it at 1.5 V.
Kreutter: Magnetism
Connected to
what?
5. Hold the wire vertically so it passes through the paper held
horizontally
6. Hold the compass as close as possible to the wire and move it around the
circumference of the wire.
7. Draw a diagram like this one, showing the orientation of the compass.
Connected to
what?
8. Increase the voltage to 2.2 and then 3 V. Does the compass react more strongly?
9. Indicate what the wire coming through the top is connected to, what the wire coming out the bottom is
connected to.
Part III: Visit all the stations. Answer questions, draw diagrams as required.
Station 1. Connect the ends of the pink coil of wire to the power source. With power off, put your compass along
the length of the coil. Draw a diagram of the circuit, including the orientation of the compass needle and the Earth’s
field.
a. Set voltage at 1.5 V. Turn the power on. What did you observe about the position, orientation of the compass
needle? Draw a new diagram showing the compass needle position. On your diagram show what the ends of the
wire were attached to.
b.
Move the compass to the other side of the coil. What did you observe?
Kreutter: Magnetism
c.
Turn the power off. What did you observe?
d.
Put the compass inside the coil. Turn the power on. Draw a diagram of the coil, compass, etc. Show the
position/orientation of the compass with the power on and off.
e.
Place the compass outside the coil but near the end. Move the compass around the end and note the position of
the needle at the various locations. Draw a diagram.
f.
Draw an overall diagram of the magnetic field around the pink coil (a solenoid).
g.
What variables could you change in Station 1 and 2 that would change the strength of the magnetic field?
Station 2. This device has three different circuits on one board.
A. Large Loop
Kreutter: Magnetism
a. Connect the large single loop to the power source. With power off, put your compass along the length of the wire.
Draw a diagram of the circuit, including the orientation of the compass needle and the Earth’s field.
b. Set voltage at 1.5 V. Turn the power on. What did you observe about the position, orientation of the compass
needle?
c. Move the compass all along the wire, around the circumference of the wire. Hold it in the air if necessary. Draw
a new diagram showing the magnetic field around the wire.
B. Small loop
a. Connect it to the power source. With power off, put your compass along the length . Draw a diagram of the
circuit, including the orientation of the compass needle and the Earth’s field.
b. Set voltage at 1.5 V. Turn the power on. What did you observe about the position, orientation of the compass
needle?
Kreutter: Magnetism
c. Move the compass all along the wire, around the circumference of the wire. Hold it in the air if necessary. Draw
a new diagram showing the magnetic field around the wire.
C. Multiple small loops
a. Connect it to the power source. With power off, put your compass along the length . Draw a diagram of the
circuit, including the orientation of the compass needle and the Earth’s field.
b. Set voltage at 1.5 V. Turn the power on. What did you observe about the position, orientation of the compass
needle?
c. Move the compass all along the wire, around the circumference of the wire. Hold it in the air if necessary. Draw
a new diagram showing the magnetic field around the wire.