7A10.35 - Photocells

Code Number:
Demo Title:
Planck's Constant
Area of Study:
Modern Physics
Photocells, Photocell Circuits, Mini Amplifier, Photocell Controlled Motor, Voltmeter.

Connect the photocell to the voltmeter and read resistance as a function of brightness shining on the photocell.

There are several battery powered photocells and photocell circuits that can be used for a variety of demonstrations.  

The photocell circuit on the small circuit board has a light that will glow brightly when under full illumination and will dim and eventually go out as the photocell is covered by a finger or a small film canister.

  • Paul Gluck and Bernd Saering, "No Time Lag in the Photoelectric Effect", TPT, Vol. 48, #5, May 2010, p. 285.
  • David L. Mott, "A Simple Transistor Demonstration", TPT, Vol. 18, #6, Sept. 1980, p. 460, also A Potpourri of Physics Teaching Ideas - Electricity and Magnetism, p. 154.
  • R. L. T. Wolfson, "Intelligent Light Bulb A Negative Feedback Demonstration", AJP, Vol. 49, #4, Apr. 1981, p. 374. 
  • Forrest M. Mims III, "Solar-Powered Night Light", Electronic Sensor Circuits & Projects, p. 140.

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