# Sample Variables & Hypothesis

### Question

How does the voltage of an AA battery change over time when used in low, medium, and high current drain devices?

### Hypothesis

If I use a AA battery in any current-draining device, then the voltage of the battery will drop over time. If I perform this test in low, medium, and high current drain devices, then the rate of voltage drop will be slowest in the low current drain device and fastest in the high current drain device.

There are two parts of this hypothesis, and thus two experiments:

• Experiment #1: Measure the voltage of fresh AA batteries as they are used in different current drain devices.
• Experiment #2: Compare the rate of voltage change between devices with low, medium, and high current drain. The second experiment does not require any more data collection, but it does require looking at the data from experiment #1 in a different way. For experiment #2, graph the data with the voltage on the y-axis and time on the x-axis for each type (low, medium, high) of current drain device.

### Variables

Experiment #1:
• Independent Variable: Time (how long each battery operates in a given device)
• Dependent Variable: Voltage
 Experimental Group Controlled Variables for Each Group Low current drain Same portable CD player Play the same music track Play at the same volume level Medium current drain Identical flashlight Identical light bulb High current drain Same camera flash All groups Battery size (AA) Constant temperature (A battery works better at a warm temperature.) Battery brand Voltmeter

Experiment #2:
• Independent variable: Type of current drain device (as quantified by low, medium, and high)
• Dependent variable: Voltage (same as experiment #1)
• Controlled variables: Same as outlined in the table for experiment #1