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Lab #8 - Faraday Induction & Lenz’s Law
Name: _______________
Copyright R Mahoney 2013
The purposes of this lab are: 1) to qualitatively evaluate Faraday's Law, using
both a finely and coarsely wound coil, and 2) to test your understanding of Lenz's
Law.
1. Hook up the galvanometer to a battery and resistor, as shown:
Quickly connecting and disconnecting the negative side of the battery, verify that
a conventional current going through the galvanometer moves the needle "like a
tree bending in a stiff wind".
2. Hook up the galvanometer and the finely wound coil as shown:
3. Use one of the unmarked magnets provided to induce a voltage and current in
the coil, according to the procedure given below. For each step, give the
direction and size of the galvanometer deflection. Use masking tape to mark one
side of the coil as “up”, and one side of the magnet as “side one” to avoid
confusion and inadvertent errors.
a) Coil up, side one of magnet:
Procedure
Direction
Magnitude
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Pull magnet up from coil
Slowly
Quickly
Push magnet down towards coil
Slowly
Quickly
b) Coil up, side two of magnet:
Pull magnet up from coil
Slowly
Quickly
Push magnet down towards coil
Slowly
Quickly
c) Coil down, side one of magnet:
Pull magnet up from coil
Slowly
Quickly
Push magnet down towards coil
Slowly
Quickly
d) Coil down, side two of magnet:
Pull magnet up from coil
Slowly
Quickly
Procedure
Direction
Magnitude
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Push magnet down towards coil
Slowly
Quickly
3. What conclusions can you draw from your qualitative observations about the
above galvanometer deflections?
4. Try any of the above procedures with the coarsely wound coil. Are the results
the same for deflection directions? Are the results the same for deflection
magnitudes?
5. Now hook up the galvanometer to the "400 winding transformer coil" provided.
Notice the markings on the coil showing the handedness of the coil's windings
(clockwise or counterclockwise, as viewed from above). Now use the magnet
provided to induce a current through the galvanometer (e.g., side one of the
magnet, going towards the marked side of the coil). Using the direction of the
deflection of the galvanometer's needle, and Lenz's Law, determine which side of
your magnet is the North Pole. Is it side one or side two? ________ Now use
the compass provided to determine if you were right about this determination.
Were you?
6. State two non-trivial systematic errors for this experiment.