Hot Bulbs. Key Words: Incandescent, Fluorescent, Watt

Transcription

1 Hot Bulbs Key Words: Incandescent, Fluorescent, Watt Getting Started: 1. Read the Introduction and Challenge to Activity 67, Hot Bulbs, in your Student Book. 2. Think of all the different types of light bulbs you have seen. What are some reasons that one light bulb may be hotter than another light bulb (one light bulb produces more heat than another)? 3. In this activity, you will investigate the efficiency of a light bulb, which is the ratio of how much useful energy output you get from the light bulb compared to the energy put into it. That shows how good the light bulb is at being a light. If the light bulb were perfect at transforming electrical energy to light energy, what percentage of the energy input would wind up as useful light energy? 4. If the light bulb is not perfect at transforming electrical energy to light energy, what happens to the rest of the energy? 5. Some people think that holding a thermometer next to a light bulb will accurately measure the amount of thermal energy given off. However, much of that thermal energy will be lost in the air. Therefore, the best way to accurately measure the amount of thermal energy released by the light bulb is to submerge the light bulb in water, and measure the temperature change of the water. The thermal energy released by the bulb will be absorbed by the water as it will be a closed system. Safety Note: Do not try this investigation with any other kind of battery or electrical energy source without consulting your teacher. Never, under any circumstances, place plugged- in electrical appliances in or near water.

2 Procedure: 1. Read Procedure Steps 1o 9 in your Student Book. Your classmates completed this Procedure. Click this link to view the Labsent video for this activity. Be sure to record the data as you watch in the table you copy below (as directed to in Procedure Step 3). Data: Describe the Control Set- Up seen in the video (Procedure Step 5):

3 2. Read and complete Procedure Steps in your Student Book. Show your calculations below. 3. Complete the After column for Questions 8-11 on Student Sheet 53.1, Anticipation Guide: Energy Ideas. Analysis Questions: 1. Answer the following questions about the control in Cup E. a. Why should you use a control in an experiment? b. What did you say should be placed in the control cup? Explain why. c. What measurements did you think should be taken? Explain why. d. What did the results of the control tell you?

4 2. A typical light bulb is about 5% efficient at producing light energy. Does your calculation agree with this? Explain why you think your calculation is or is not the same. 3. Are light bulbs better at producing light or heat? Explain, using results from this experiment.

5 4. Do you think you would be more concerned about inefficient bulbs in a home that is in a warm climate or a colder one? Explain. 5. The bulb used in this activity is an incandescent light bulb. Look at the table on page D- 85 of your Student Book that compares an incandescent light bulb to other kinds of bulbs that are about the same brightness. Answer the following questions: a. Which is the best light bulb? Using the table, explain the evidence that helped you decide. b. Why do you think people buy more incandescent light bulbs than any other bulb?