Question

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 controlled variables for their investigation? choose 2 answers: a battery voltage b number of turns of wire around the nail c paperclip size d number of paperclips that hang from the nail

Explanation:

To determine controlled variables, we identify factors that must be kept constant to test the effect of the independent variable (number of wire turns) on the dependent variable (electromagnet strength, measured by paperclips).

• Option A (battery voltage): Voltage affects current, which impacts electromagnet strength. Keeping it constant ensures the only change is wire turns.
• Option C (paperclip size): Consistent paperclip size ensures the measurement of "strength" (number of paperclips) is fair, as different sizes would have different weights/attraction needs.
• Option B is the independent variable (tested), and Option D is the dependent variable (measured), so they are not controlled.

Answer:

A. battery voltage, C. paperclip size