Question

a student plans to investigate how different factors affect the rotation rate (rpm) of a hand - made motor when connected to a battery. the student will test a different variable in each investigation: the voltage of the battery (v), the number of loops used in the wire coil, and the number of magnets used below the loops. the first table shows details and predictions for investigation 1. the second table shows the details and predictions for investigation 2. how should the student design investigation 3 to finish testing the factors that affect the rotation rate of a motor? a increase the battery voltage to 3.0 v keep the number of wire loops at 10 loops keep the number of magnets at 1 magnets b keep the battery voltage at 1.5 v keep the number of wire loops at 5 loops increase the number of magnets to 2 magnets c increase the battery voltage to 4.5 v decrease the number of wire loops to 1 keep the number of magnets at 1 magnets d keep the battery voltage at 1.5 v increase the number of wire loops to 15 loops

Explanation:

Step1: Identify the variables tested

In investigation 1, the variable is battery voltage. In investigation 2, the variable is the number of wire loops. So, investigation 3 should test the number of magnets.

Step2: Apply the control variable method

To test the number of magnets, keep battery voltage and number of wire loops constant (as in previous trials where other variables were tested). Looking at the initial values (e.g., from trial 1 where other factors were baseline for one variable test), battery voltage \(1.5V\) and wire loops \(5\) (as in trial 1 of investigation 1 where magnet number was \(1\) initially, now we change magnet number).

Answer:

B. Keep the battery voltage at \(1.5V\), keep the number of wire loops at \(5\) loops, increase the number of magnets to \(2\) magnets.