Question

a student is measuring the effects of an electric circuit on a compass, and he is testing to see if increasing the current will cause the compass needle to change its direction faster. he does one trial using a 9 - volt battery and another trial using a 1.5 - volt battery. he takes accurate data. based on good experimental design, what would improve his experiment? he should use only one battery but do several trials, using different circuit designs to ensure he has appropriate test groups. he should repeat the test with three additional batteries of varying voltages to demonstrate the reproducibility of results. he should use batteries of the same voltage but from different manufacturers to show he has used different variables. he should add a nonworking compass to act as a control.

Explanation:

In a good - experimental design, to improve reliability and validity, more data points are needed. Repeating the test with additional batteries of varying voltages helps demonstrate the reproducibility of results. Using only one battery with different circuit designs changes the focus of the experiment. Using batteries of the same voltage from different manufacturers doesn't address the main variable of voltage affecting the compass. A non - working compass as a control is not relevant as the experiment is about the effect of an electric circuit on a working compass.

Answer:

He should repeat the test with three additional batteries of varying voltages to demonstrate the reproducibility of results.