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Home Concept Builders Fundamentals: Relationships and Graphs Experiments and Variables Help Help 7

Experiments and Variables - Questions 7 Help

Experiments are commonly performed in order to determine the effect of one variable (the independent variable) upon another variable (the dependent variable). When designing such an experiment, it is important to identify all possible variables that might effect the outcome on the dependent variable. Once done, hold all variables constant with the exception of the independent variable. Make systematic and controlled changes in the independent variable and measure the effect upon the dependent variable.

There are several versions of this question that differ only in terms of the randomized order of the answer options. Here is one of those versions:
 

Version 1:

A student lab group is brainstorming the design of an experiment that uses a mini light bulb and a light meter to determine how light intensity varies with the distance from the source. Which Post-it note describes the most effective design?

  1. Turn off the room lights and turn on the light bulb. Place the light meter 25.0 cm from the bulb. Measure the light intensity. Add a second light bulb and measure the new intensity. Repeat trials for three and four light bulbs, being careful to keep the light meter the same distance away from the bulbs.
  2. Turn off the room lights and turn on the light bulb. Place the light meter 10.0 cm from the bulb. Measure the light intensity. Add a second light bulb and move the light meter 20.0 cm away from the bulb. Measure light intensity. Repeat trials for different number of bulbs. Each time you add a bulb be sure to add another 10.0 cm to the distance. Record light intensities for each distance.
  3. Turn off the room lights and turn on the light bulb. Place the light meter 10.0 cm from the bulb. Measure the light intensity. Repeat the measurement of intensity with the light meter 20.0 cm away. Repeat trials with distances of 30.0 cm and 40.0 cm.
  4. Turn off the room lights and turn on the light bulb. Place the light meter 10.0 cm from the bulb. Measure the light intensity. Obtain a new bulb that has a different brightness. Place the light meter at 10.0 cm and measure the new light intensity. Repeat these measurements for different bulbs but be careful to control the distance from trial to trial.

You are going to have to do some reading here. As you read, make sense of the words. You are looking for a procedure that is going to allow one to determine the effect that distance from a light source will have upon the light intensity. Such a procedure will be careful to keep everything constant and controlled except for the distance. And from trial to trial, the light intensity will be measured.

Bad experimental designs will fail to control other variables besides the distance or will fail to measure the light intensity. So read carefully and eliminate the poor designs and select out the design that isolates distance as the independent variable and the only variable that is changed.

Sorry. We're pedaling as fast as we can but as of this writing we do not have any Tutorial information on the topic of experimentation and variables.

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