Lab 5. Challenge.

Challenge 1:   Dependence of the motor coil frequency on the magnetic field magnitude (bonus 10%).

You already measured the motor coil frequency  for the black magnet (with one  resistor short-circuited). Let us call this frequency  from now on (we will keep one  resistor short-circuited). Shut down the motor without touching the coil and axle supports by interrupting the circuit. Carefully replace the black magnet with the blue one. Make sure the blue magnet is in the same position and with the same pole orientation as the black magnet. Restart the motor (the coil should rotate in the same direction as before). Measure the frequency  of the motor. Include the screenshot of your signal into your report.

Apply the simple model we introduced in Experiment 5 to derive . Compare the ratio  with the ratio  that you obtained in Experiment 3. Comment on the validity of the model.

Challenge 2:   High frequency motor (bonus f%).

Make your motor most efficient. The goal is to increase its frequency so that it is 10Hz or more. If the frequency of your motor is at least 10Hz you receive a bonus – the number of %s that is equal to the frequency of your motor in Hz.  

Tip 1: you may find all suggestions listed in p.7 of Experiment 5 useful. Tip 2: you may tweak the shape of the coil as long as it remains of generally oval shape.
Rules of the game: you may only tweak the coil, axle supports, and magnet position/orientation. The coil should remain of the same general shape (circle/oval) with the same number of turns (n=3.5). No additional equipment/parts are allowed. You can only use one magnet (black), you may short-circuit one of two resistors but another one should remain in the circuit (you need it to register voltage across it). You should use the same single AA battery – no additional voltage sources are allowed.

Create a simple video of your working electric motor, upload it on Youtube (make it “Unlisted”) and include the link to your video into your report. No fancy video editing is needed.
Include the screenshot of your signal (voltage across  resistor) with its FFT analysis that shows frequency clearly identified - in Figure E.16 format.