Christmas Lights and LEDs

Connect a Christmas light to the apparatus by using the terminals that are used for the voltmeter. Then, adjust the potentiometer to vary the voltage applied across the Christmas light. When you are finished, answer the following questions:

1. What is the color of light emitted by the Christmas light?
2. If the color of light changes with voltage, how does it change?
3. What is the threshold voltage of the Christmas light and the voltage at maximum brightness?
4. How does the brightness of the Christmas light change with voltage?
5. Based on your observations of the Christmas lights, make a prediction on whether the lights are incandescent lamps or LEDs. Explain your reasoning.
6. Record your measurements, observations, and answers to the questions in the space provided here.

A final comparison between the LEDs and Christmas tree lights involve their colors. Summarize the similarities and differences in the color of light emitted by considering the following questions:

1. Can you determine the color that will be emitted before you turn on a Christmas tree light and an LED? Why or why not?
2. What property of the light source seems to determine the color?