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?

Answer 1

Answer: The type of batteries

Explanation: Your testing the brightness of the bulb nothing has anything to do with the batteries