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Transcript
Exercise 5: A nightlight Names: _________________________________________ Create the following “nightlight” circuit on your breadboard: Questions: 1. A photoresistor is a light sensitive resistor. When it’s dark, the photoresistor’s resistance is large; when it’s light, the photoresistor’s resistance is low. Measure and record the photoresistor’s resistance and the current flow through it in both ambient light and in the dark. Cover the top of the photoresistor to simulate “dark”. Dark Resistance of photoresistor:_________ Current through photoresistor: ________ Ambient Light Resistance of photoresistor:__________ Current through photoresistor: ________ 2. Using the measured values above along with Kirchoff’s laws and Ohm’s law, calculate the current passing through the LED and the voltage drop across the LED in both ambient light and dark. Show your work below. LED in Dark: Current:_______________________ Voltage:_______________________ LED in Ambient Light: Current:_________________________ Voltage:_________________________ 3. Verify your calculations with measurements; i.e., measure and record the voltage and current calculated above. LED in Dark: Current:_______________________ Voltage:_______________________ LED in Ambient Light: Current:_________________________ Voltage:_________________________ 4. Is the performance of the nightlight consistent with what you know about LEDs? Explain. Extra Credit: Try modifying the circuit to improve the performance of the “nightlight.” If you are able to create a better nightlight, draw the circuit for your improved nightlight below. (Be sure to include a resistor (>=470 Ohm) between the power sources and the LED.)