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Home Concept Builders Fundamentals: Relationships and Graphs Experiments and Variables Help Help 8

Experiments and Variables - Questions 8 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 an ammeter (measures current) and different resistors to determine the effect of the resistance of a resistor upon the current in a simple circuit. Which Post-it note describes the most effective design?

  1. Put a 10.0-ohm resistor in the circuit. Measure the current in the circuit. Replace the 10.0-ohm resistor with a 20.0-ohm resistor. Measure the new current. Continue replacing the resistor with a different resistor of known resistance. Measure the current for each resistor. Record all data.
  2. Put a 10.0-ohm resistor in the circuit. Measure the current in the circuit. Move the ammeter to a different location in the circuit. Measure the current at this new location. Continue moving the ammeter to different locations within the circuit but be careful to keep the resistor in a fixed location. Measure and record all current values.
  3. Obtain a variety of batteries and build several circuits. Make sure that each circuit has at least one resistor and make sure that the resistance values are different in the different circuits. Place various ammeters in each circuit. Measure the number of batteries and the current for each of the circuits. Record the resistance values used in each of these circuits.
  4. Put a 10.0-ohm resistor in a circuit with a single D-cell. Measure the current in the circuit. Add a second D-cell and measure the current with two D-cells. Repeat trials for three, four, and five D-cells, being careful to get accurate current measurements for a fixed amount of resistance in each 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 resistance will have upon the current. Such a procedure will be careful to keep everything constant and controlled except for the resistance. And from trial to trial, the current will be measured.

Bad experimental designs will fail to control other variables besides the resistance or will fail to measure the current. So read carefully and eliminate the poor designs and select out the design that isolates resistance 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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