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ELE 100 Introduction to Engineering
Magnetic Fields Lab
In magnetism, direction is defined by naming one pole of a magnet the north pole and the other
the south pole. The magnetic field of the earth was known in early times in that a magnetite (a
mineral, naturally occurring material) needle floating on water would line up in a north-south
direction. A compass is a simple tool that can be used to examine a magnetic field. Carefully
observe and record all observations.
Part A
With the magnet and compass on the table as shown, explore
around the magnet with the center of the compass about 2
centimeters away from the magnet. How does the deflection of the
compass change as you do that? When done, place the magnet on
the front table so it doesn’t interfere with the next experiment.
Part B
We will use the power supply as a current supply. Set the voltage of the power supply to 1 volt.
Turn the current coarse limit down to as low as it goes (counterclockwise). Place the wooden wire
support so the wire is horizontal. Connect the end of the wire with a dot on the post to the positive
terminal of the power supply. Connect the other end of the wire to the negative terminal. Adjust
the current to about 2 amperes. Disconnect the wire from the positive terminal. Assuming that
positive current comes out of the positive terminal, sketch which direction positive current flows
through the wire.
Line up the compass and the wire so that the wire is oriented in a north-south direction, i.e. the
compass needle is pointing in the direction of the wire, and so that the compass is on or slightly
above the wire and midway between the wooden posts. Keep the compass horizontal at all times
so that the needle can rotate freely. Connect the wire to the positive terminal and record the
direction of the compass (north, south, east, west, or something in between). Move the compass to
a position just below the wire. What is the direction of the needle?
With the compass just above the wire, raise the compass slowly, keeping horizontal. How does
the direction of the needle change? Disconnect the wire from the supply. Sketch what you
observed with pictures of the wire and the compass.
Part C
Turn the board so the wire is vertical. Keeping the compass horizontal and next to the wire, move
the compass around the wire. How does the direction of the needle change?
Reverse the connections of the wire to the supply. Record the direction of the positive current in
the wire. Repeat the exploration with the compass around the wire. Record your observations.
Assume that the compass needle is lining up with magnetic lines of force in the space surrounding
the magnet or the wire. Sketch those lines of force. How does the strength of the magnetic field
change as distance from the magnet or the current increases? Discuss your observations. What
conclusions can you draw?
ELE 100
Magnetic Fields Laboratory, Continued
Part D
On the power supply, set the voltage to 1.0 volts and turn the current limiting knobs fully
counterclockwise. Connect one end of the wire coiled around the bolt to the negative
terminal and the other end to the positive terminal. Increase the current to about 1.0
amperes.
Explore the magnetic field around the bolt with the compass in the same manner as you
explored the magnetic field around the permanent magnet. Record your observations.
Keeping the magnet in the same position and orientation, reverse the connections of the
wires to the power supply. Explore the magnetic field around the bolt and record your
observations. Disconnect the wires from the power supply. Compare these observations
with those in the first instance.
What do you conclude from these observations? Write your conclusions on a piece of
paper.
Part E
Get a permanent magnet. Merge two teams so you have two magnets.
Place one magnet on the table surface with the rolling surface on the table. Holding this
first magnet in place, gently bring a flat end of the second magnet toward a flat end of the
first. What happens? Bring the other flat end of the second magnet toward the same flat
end of the first. What happens?
Repeat this procedure, but don’t hold the first magnet in place. What happens?
What do you conclude from these observations?
Write a short paper summarizing what you observed and what you learned about
permanent magnets, electromagnets, and magnetic fields.