5C30.38 - Capacitor - Charge & Discharge - Genecon Generator

Code Number:
Demo Title:
Capacitor - Charge & Discharge - Genecon Generator
Charging and Discharging of a Capacitor
Area of Study:
Electricity & Magnetism
Genecon Generator, 1 farad capacitor.

The Genecon generator and the 1 farad capacitor make a fine demo because the generator will also run as a motor.  This means that you can show a relationship between energy put into a capacitor and that taken out.  Hook the generator to the 1 farad capacitor after making sure the capacitor is discharged.  Charge the capacitor and count the number of turns you put in.  Let go of the generator handle and the stored energy in the capacitor will make the generator run as a motor.  Count the number of turns the handle makes in this cycle.  There will almost be a direct 1 to 1 relationship (ie. 10 turns put into the capacitor, 9 1/2 turns out).

Interestingly enough the handle will turn in the same direction that you were turning it when you charged the capacitor.

Capacitor: you crank the generator handle as you charge it and current flows into it.  You have to apply a torque to because the current flowing in the generator makes it want to act like a motor in turing in the opposite direction.  You release the handle and now the capacitor discharges and current flows in the opposite direction.  This causes the handle to turn in the origional direction.

Coil: you crank the generator applying a torque.  Again, because the generator acts like a motor it resists your efforts forcing you and to do work.  You release the handle, the current keeps flowing in the same direction (Lenz's Law).  This results in a torque in the same direction that registered your efforts origionally and the handle changes direction.

Details of why this is can be found in the file.

A subtle comparison can be made between an inductor and a capacitor using a hand crank DC generator.  When connected to the capacitor, the generator is hard to crank at first and gets easier to crank as you continue.  When you quit cranking the generator will keep going on its own in the same direction as you cranked it.  Do the same with an inductor and it gets harder to crank as you continue and when you let go, it stops and turns in the opposite direction you originally cranked it.

  • Carl E. Mungan, "...And Hand-Cranked Induction", TPT, Vol. 52, #9, Dec. 2014, p. 518.
  • Art Hovey, "Hand-Cranked Intuition", TPT, Vol. 52, #9, Dec. 2014, p. 518.
  • Carl. E. Mungan, "Motor Demonstration Using a Hand-Cranked Genecon",  TPT, Vol. 52, #7, Oct. 2014, p. 422.
  • Robert Ehrlich, "9.4, A Generator and a Capacitor", Why Toast Lands Jelly-Side Down, p. 149.
  • Tap-l conversations, Genecon - Charge a Cap and a Coil, 9-25-2018.

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