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== Activities ==
=== Part 1 - Potentiometer ===
* Locate your 10K potentiometer. It should say "10K" on the front of it.
** What is the measure between "A" and "B"? does it change as your turn the knob?
[[Image:Pot_divider_10k.png | 200px]]
[[Image:Pot_divider_1K.png | 200px]]
=== Part 2 - Light Sensor ===
* Photoresistor as variable resistance
** measure the "light" resistance of your photoresistor
** Set up a voltage divider with the photoresistor and a 10K resistor. You can take your circuit from before and replace the potentiometer with the photoresistor. What range of output voltages can you get by covering or uncovering the photoelement?
[[Image:Photoresistor_v_out.png| 200px]]
=== Part 3 - Transistor Driver ===
* Get out your transistor. It should say "TIP 120" on the front of it.
[[Image:Tip120-TO-220-3.jpg | 200px]] [[Image:Tip120_pins.png| 200px]] [[Image:Transistor_EBC.png | 200px]]
* Connect a transistor to control the brightness of a bulb by turning the knob of a potentiometer.
[[Image:Pot_transistor_bulb_driver.png]]
* Subsistuting Substituting a photoresistor in place of the potentiometer, make a light "phobic" and light "philic" circuit, as in the diagrams below.
[[Image:Positive_feedback.png | 400px]]
[[Image:Negative_feedback.png | 400px]]
