Question

a group of students builds an electromagnet by turning wire around a nail, and then connecting the ends of the wire to a battery. the students can hang some number of paper clips from the nail, as shown below. the students predict that increasing the number of turns of wire around the nail will increase the strength of the electromagnet. they plan an investigation to test their prediction. what should they select as the independent variable for their investigation? choose 1 answer: a number of paperclips that hang from the nail b paperclip size c battery voltage d number of turns of wire around the nail

Explanation:

To determine the independent variable, we recall that the independent variable is the one manipulated by the experimenter to observe its effect on the dependent variable. The students' prediction is about how increasing the number of wire turns affects the electromagnet's strength. So they will manipulate the number of wire turns (the independent variable) and observe changes in the number of paperclips (dependent variable). Option A is the dependent variable. Options B and C are not the variable being tested in this prediction (they would be controlled variables or unrelated here). Option D is the variable the students plan to change to test their prediction.

Answer:

D. number of turns of wire around the nail