Procedure and Tasks


1.     Measure induced electro-motive force and the terminal velocity with the oscilloscope. This is most conveniently done by using the short Cu tube. One should connect the two coils (in parallel) to the oscilloscope and then drop the magnet down the tube. The oscilloscope will measure the induced voltage as a function of time. Use this plot to determine if there is any difference in the strengths of the different magnets by checking the maximum value of the voltage and the terminal velocity.

2.     Use a 4-point contact method for measuring the conductivity of the short tube.

3.     Determine dipole moment strength from induction signal (Again use position of the maximum).

4.     Determine dipole moment strength from the terminal velocity.

5.     Measure the force between two dipole moments as a function of separation distance. This can be performed with the aid of a digital scale. Plot the force as a function of distance.

6.     Determine dipole moment strength from the force between the two (identical) dipoles.

7.     Cool short tube with liquid nitrogen and check for any qualitative differences in the behavior of the experiment. Such as the new terminal velocity.


Oscilloscope operating instructions

1.     Connect the pickup coils on the metal tube to the oscilloscope.

2.     Turn on the oscilloscope. Make sure every switch is on the right position as the graph shows. In particular the input has to be on dc-voltage.

3.     Press "store" button on upper-right corner of the front panel to display a continuous line. (If no display, try to adjust the bean intensity).

4.     Drop the magnet into the vertical tube. Press the "save/continue" button on the top-right corner when both of the two pulses are shown on the screen. Adjust the voltage scale (vertical axis) or the time scale (horizontal axis) if necessary.

5.     To measure the voltage amplitude or the time difference, use the cursors on the top of the panel.

6.     Press "save/continue" button again to continue the experiment.

7.     In the Mode function, choose: CH1, NORM, ALT.

8.     Set time scale "SEC/DIV" in range 0.1 ~0.5s.

9.     Set the voltage range of Channel 1: CH1 "VOLTS/DIV" to 5mV.

10. When the pulse signal appears, press "save" in "ACQ" function to catch the signal.

11. In cursor function, press "on" to activate cursors. Press "ΔV1/ΔV1" to measure voltage difference. Or press "ΔT/1/ΔT" to measure time difference. Two measure lines will appear on the screen.

12. Adjust the knob on the left side of the cursor function to move the cursor line. Press this knob to select active cursor.