Voltage

To vary the energy supplied to the incandescent lamp, turn the knob of the potentiometer by using the tiny screwdriver. Either end of this screwdriver can be used. However, the end where the blade of the screwdriver is recessed in a cavity is easier to use. The diagram below shows how to increase and decrease energy.

The voltage measured by the meter is directly related to energy, so you will use it in the observations. As you vary the voltage, make sure to record your observations about the change in the emitted light. When you have finished, you should be able to answer the following questions.

1. What is the color of light emitted by the lamp?
2. How does the color of light change with voltage?
3. What is the voltage when the lamp barely emits light, called threshold voltage, and the voltage is at its maximum brightness?
4. How does the brightness of the lamp change with voltage?

Record your measurements, observations, and answers to the questions in the space provided.