Question

A student examines the effect of the number of D batteries in a closed circuit on the brightness of a light bulb. In the experiment, four circuits were built with 1, 2, 3, and 4 batteries respectively. For each trial, the brightness of the light bulb was measured using a light meter. Which variable should the student keep constant?
the type of batteries


the number of batteries


the brightness of the light bulb


the data collected from the light meter

Answer 1

The correct answer is the Type of batteries

Explanation:

In an experiment, it is normal the researcher modifies one variable, in this case, the number of batteries (independent variable), and this variable affects the variable tested, in this case, the brightness of the bulb (dependent variable).

However, other factors or variables should be constant to guarantee the results are reliable. In this context, one factor that the student should keep constant is the type of batteries he uses because this is not one of the main variables and therefore it is not expected he changes this on purpose or this is affected by other variables. Moreover, by making any change the experiment can be negatively affected. For example, batteries might differ in their power capacity this can affect the brightness of the bulbs.