Module 9
PlanningGuide

Lab 3.5

Lesson 3.5
Lesson 3.6
Lesson 3.7
Lesson 3.8
Lab 3.5
Lab 3.6
Lab 3.7
Lab 3.8
Project 9

Physics Lab 3.5 Flux

Overview
The purpose of this laboratory class is to show that the amount of radiation passing through a particular area decreases with the square of the distance from the source.

Experiment
Using a solar cell and a multimeter, measure the variation in current with distance as the cell is moved closer and further from a light source.
(Alternatively: Observe the variation of brightness as a piece of white paper is moved closer to and further from a light source.)

Experiment : Solar Cell and Multimeter

Equipment

• Solar cell
• Multimeter
• Tape measure
• Light bulb / light source

Procedure

1. Set the multimeter to measure current. (milliamps)
2. Place the tape measure so that is can be used to measure distance from the light bulb.
3. Measure the reading on the ammeter with the solar cell held 10 cm from the light bulb.
4. Move the cell 5 cm further from the bulb and take the ammeter reading
5. Repeat step 4 a number of times.
6. Plot the variation in current reading with distance from the light bulb.

Results

Calculation

Taking the ammeter reading at 10 cm from the bulb, calculate what the reading would be for each of the distances used in 5 above. Assume that the reading should decrease with the square of the distance.

For example:

If the reading at 10 cm is 200 milliamps, the reading at 15 cm should

be 200 x (10² ¸ 15²) = 0.444 x 200 = 88.89 milliamps.