You will need the following parts from your kit:1. Breadboard

2. Photocell

3. 1 LED (light emitting diode)

4. 9 volt battery lead

5. 9 volt battery

Use this schematic to construct the experiment.

+

-

Flow of current

Flow of current

9 volts

Quick Check:

Your circuit should like this one.

But you should be able to build it looking at the schematic alone!

Photocell

Copy and label all the components of the schematic in your notes.

The arrows are part of the schematic

symbols

1. Connect the 9 volt battery.

2. Observe the brightness of the LED.

3. Cover the photocell with your finger.

4. Observe the brightness of the LED.

5. Carefully shadow the photocell so that a little amount of light is able to strike the cell.

6. Observe the brightness of the LED.

Troubleshooting:

1. If the LED’s do not light up, check to make sure it is in correctly.

2. Check the battery. Does it have voltage?

3. Are there any breaks in the circuit?

4. You may need to get a flashlight or other bright light if the classroom is too dark.

Fill in the blanks. 1. The greater the electron flow the ________ the

light.2. Electrons flow from the battery through the ____,

then the ______, finally back to the ______.3. The _________ the resistance, the fewer electrons

will flow. 4. Photocells adjust the amount of _________

according to the amount of _______ that strikes the cell.

5. How can you use a photocell to make a LED get dimmer?6. Why do you suppose that there is not a resistor in this circuit?7. 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.

8. Which is a photocell more like: a resistor or a potentiometer? Why?

9. In complete sentences, write what you learned about a photocell in a circuit.