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How a Photocell Works.

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Presentation on theme: "How a Photocell Works."— Presentation transcript:

1 How a Photocell Works

2 Take Inventory of your Parts
You will need the following parts from your kit: Breadboard Photocell 1 LED (light emitting diode) 9 volt battery lead 9 volt battery

3 Use this schematic to construct the experiment.
Build the Circuit Use this schematic to construct the experiment. The arrows are part of the schematic symbols Flow of current Photocell + 9 volts - Quick Check: Your circuit should like this one. But you should be able to build it looking at the schematic alone! Flow of current Copy and label all the components of the schematic in your notes.

4 Do the Experiment Connect the 9 volt battery.
Observe the brightness of the LED. Cover the photocell with your finger. Carefully shadow the photocell so that a little amount of light is able to strike the cell. Troubleshooting: If the LED’s do not light up, check to make sure it is in correctly. Check the battery. Does it have voltage? Are there any breaks in the circuit? You may need to get a flashlight or other bright light if the classroom is too dark.

5 The Theory: Fill in the blanks.
The greater the electron flow the ________ the light. Electrons flow from the battery through the ____, then the ______, finally back to the ______. The _________ the resistance, the fewer electrons will flow. Photocells adjust the amount of _________ according to the amount of _______ that strikes the cell.

6 Observations: What did you learn?
How can you use a photocell to make a LED get dimmer? Why do you suppose that there is not a resistor in this circuit? How can you measure how much resistance the photocell has under both dark and light conditions? What tool is used to measure resistance? Write down what you think the minimum and maximum resistance of your photocell is. Which is a photocell more like: a resistor or a potentiometer? Why? In complete sentences, write what you learned about a photocell in a circuit. What did you learn?


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