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Lab 22: A Magnetic Menagerie
Physics
A M Kolchin
In this lab we’ll go around to various stations, read the directions of what to
do at these stations, and record our observations. We’ll account physically
for those we can, and compare notes on the others before discussing the
physics involved. Write in full sentences so that a person who doesn’t know
what’s going on can understand your observations.
You need not visit the stations in order. If a station is occupied, go to
another.
STATION 1: Magnetic Fields of Magnets
Here you see some configurations of magnets hidden by green trays. Use the
compass to identify the poles of the magnets. Draw each configuration, the
field lines, and identify (label) the poles.
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STATION 2: Right Hand Rule #1: The direction of a Magnetic Field
due to a Current.
CAUTION: ALWAYS SHUT OFF THE POWER SUPPLY WHEN
ADJUSTING CONNECTIONS AT THIS STATION.
Here you see a thick brass wire passing through a platform on which
compasses are resting comfortably.
Hook up the alligator clips so that the current is going UP through the
platform. Tap the compasses gently without touching the brass wire. Is the
right hand rule obeyed? Draw what you see, including the direction of the
current and the directions in which the compasses point.
Now hook up the alligator clips so that the current is going DOWN through
the platform. Tap the compasses gently without touching the brass wire. Is
the right hand rule obeyed? Again, draw what you see, including the
direction of the current and the directions in which the compasses point.
STATION 3: The Electromagnet and Magnetic Domains
PLEASE DO ALL STEPS IN ORDER
Here you see a solenoid resting comfortably on a soft bed of powdered iron
surrounded by a ring of compasses.
1. Hook the red alligator clip to the (+) terminal of the battery and the
black alligator clip to the (-) terminal. Does the solenoid act like a
magnet? Do the compasses seem to care?
2. Now insert the nail into the solenoid. Does the solenoid act like a
magnet? Do the compasses seem to care?
3. Describe and draw what you see (The solenoid, the compasses,
identify the North and South poles of the solenoid). How does this
relate to our discussion of magnetic domains?
PLEASE DISCONNECT THE ALLIGATOR CLIPS AND REMOVE THE
NAIL BEFORE LEAVING THE STATION.
STATION 4: Natural Magnets and Heavy Considerations.
Some rocks contain a magnetized mineral called magnetite. Such rocks are
called “lodestones”, also spelled loadstone. But seriously, which of these
two specimens is the lodes tone and which is the loadstone? Iron filings are
provided for your decision making.
STATION 5: A Changing Magnetic Field causes a ______________?
Here you see a solenoid hooked up to a galvanometer. A galvanometer
consists of a needle and use of magnetic effects to register a voltage by the
swing of a needle.
1. Take the magnet and push its North Pole SLOWLY into the solenoid.
Hold it there then pull it out SLOWLY. Now repeat the action but
QUICKLY. Describe what you see.
2. Repeat the above using the South Pole of the magnet. Describe what
you see. What is different from what you observed using the North
Pole?
3. Hold the magnet (either pole) still in the solenoid. How does the
galvanometer react?
STATION 6: The Copper Tube of Time or
A Changing Magnetic Field causes a changing _________?____ which
causes a ________?_______.
Here you see a copper tube and two balls; one of steel and one of
neodymium. First, satisfy yourself that the copper itself is not magnetic
using a bar magnet.
Drop the steel ball through the tube. Then drop the neodymium ball through
the tube. What do you observe?
STATION 7: A Changing E-Field causes a ____________________?
Here you see a solenoid inside a larger solenoid. The inner solenoid is
connected to a large galvanometer. A galvanometer consists of a needle and
uses magnetic effects to register a voltage by the swing of a needle. Nearby
are two power supplies.
PART 1: The Top Power Supply.
1. Hook the top power supply to the outer solenoid with alligator clips.
Don’t worry about which is (+) and (-); we’re not looking that closely
yet.
2. Turn on the top power supply and SLOWLY turn up the voltage.
(You are causing a change in E-field in the outer solenoid.) Then turn
it down slowly. Now repeat but do it rapidly.
3. Insert the nail into the inner solenoid and repeat step 2. Also, try
lingering with the voltage up. What does the galvanometer do as you
linger?
4. Turn off the top power supply, disconnect the alligator clips, and
remove the nail.
PART 2: The Bottom Power Supply: A Function Generator
1. Hook the bottom power supply to the outer solenoid with alligator
clips. Hook the negative (black) clip first, then the red (which has a
rubber guard), but it doesn’t matter to which terminal. This power
supply (already turned on) should be set to deliver a voltage that is
changing sinusoidally between ± 10 volts with a frequency of 1 Hz.
Describe what you see.
2. Now insert the nail into the inner solenoid. Describe what you see.
3. Time how long it takes for the needle on the galvanometer to swing
back and forth; that is, what is its period? (Time 20 roundtrips and
divide by 20; what frequency is this?)