Electromagnetic Induction Lab
AP Physics – Frisby
Name______________________ date_______
Experiment 1. Poles and Fields in Relation to Direction of Current (6 sketches)
Purpose: To observe the relation between the direction of current flowing in a coil of
wire and the direction of the magnetic field (B) lines resulting from that current.
1. Mark the binding posts of one of the small coils. Connect the coil to a battery,
place a small compass somewhere closely in front of the coil along the axis. The
initial direction of the compass needle must point in a direction other than parallel
to the axis. Note the direction in which the north end of the magnetic compass
points.
2. Draw a diagram of the magnetic field created marking the direction of the needle,
the direction of the magnetic field B, the direction of the current, the binding
posts, and the polarity of each end of the coil. (2 sketches – a view from above
and a view from the front of the coil).
3. Reverse the direction of the current in the coil and see if any change takes place in
the behavior of the compass needle. Record your observations. Explain.
4. Slip a piece of soft iron into the coil and repeat steps 1-3. Draw 2 sketches of the
magnetic fields as viewed from above.
Experiment 2. Electromagnet
Purpose: To observe the operation of a coil of wire and an iron core as an electromagnet.
1. Make an electromagnet of the two coils and the cast iron strip with double core,
connecting the two coils in series. Pass the current through and test your work
with the compass. What is the polarity of the free ends of the iron?
2. Try the lifting power of the electromagnet on the square piece of iron.
3. Explain how an electromagnet works.
Experiment 3. Currents Induced by Magnetism
Purpose: To observe the effect of moving a magnetic pole into a coil of wire.
1. Check the polarity of a bar magnet with a compass. Connect the large coil to the
current probe. Note the effect of suddenly thrusting the “N” pole of the magnet
into the coil. Then, quickly withdraw the magnet. Print out the graph.
2. On the graph, draw two sketches of the set up marking the direction of the
magnetic field of the bar magnet B, the direction of the induced current, and the
direction of the magnetic field of the induced current Bi. Explain.
3. Reverse the magnet and repeat steps 1-3.
4. Very slowly bring the magnet and the coil together. What effect does the slow
motion have on the induced current?
Experiment 4. Currents Induced by Electromagnetism
Purpose: To observe the effect in a coil of wire of moving another coil of wire with a
current near to and away from the 1st coil.
Part A. Separation Effect
1. Connect a small coil to a battery using a switch. In this case, as always, current
should not be completed except when the effects are being observed.
2. Connect the terminals of the other coil to the current probe.
3. Complete the circuit in the first coil and bring this coil up immediately adjacent to
the other coil and with their axes in line. Make this movement rather quickly. Let
the first coil come to rest and then remove the coil while the current is still
flowing. Print out the graph current vs. time.
4. On the graph, draw two sketches of the set up marking
- the direction of the current and the direction the magnetic field in the first coil B;
- the direction of the induced current and the direction of the magnetic field in the
second coil Bi. Explain.
5. Repeat step 3 moving the first coil rather slowly. Compare the results to the
results from step 3.
6. Increase the distance between the two coils by ~3 cm. Repeat step 3. Compare the
results to the results from step 3.
Part B
1. With the coils close to each other, but with the current circuit not complete,
suddenly close the switch completing the circuit. Then, break the circuit quickly.
Print out the graph current vs. time.
2. On the graph, draw two sketches of the set up marking
- the direction of the current and the direction the magnetic field in the first coil B;
- the direction of the induced current and the direction of the magnetic field in the
second coil Bi. Explain.
3. With the round iron core bar in position through both coils, repeat step 1. Is the
peak current now larger or smaller than before?
4. With the round iron core bar in position through both coils, increase the distance
between the two coils and repeat step 1. Compare the results to the results from
step 3.
5. Set up the two coils with the cast iron strip with double core and repeat step 1. Is
the peak current now larger or smaller than before?
6. Repeat step 4, but now place the straight iron core over the U-shaped core. Is the
peak current now larger or smaller than before?
Summary:
1. What are the conditions under which a current can be induced in a coil that is not
connected to a battery?
2. What are the physical quantities that affect the magnitude of the induced current?