Run the Faradays Electromagnetic Lab simulation httpphetcolo

Run the \"Faraday\'s Electromagnetic Lab\" simulation: http://phet.colorado.edu/en/simulation/legacy/faraday (you will need to click the play button download it)

Go to the \"Electromagnet\" tab. There you will see a battery connected to a 4-loop coil, and a compass. Notice the direction that the compass needle is pointing. Also notice the directions of the tiny red and white magnetic field indicators.

Look carefully at the battery; you will see a slider control on the battery. Slide it all the way to the left, then to the right, then to the left again. Do this several times, without changing anything else. What effect(s) does this have on the magnetic field? (NOTE: It may help to \"Show the Field Meter\" by checking that box.) Choose all the answers that apply. Please explain how you know please if you can.

a. There is a position of the battery slider control for which the magnetic field is zero.

b. The field changes direction as you move the control all the way to the left, then all the way to the right.

c. The field alternately gets weaker, then stronger, then weaker again, then stronger again, as you move the slider back and forth.

d. The field is weaker when the battery slider control is all the way to the right than it is when the slider is all the way to the left.

e. There is no change to the field as you change the number of coils.

f. The field is weaker when the battery slider control is all the way to the left than it is when the slider is all the way to the right.

Solution

Ans)Here options a, b ,c, d ,f are corrects.
Here basically by changing the slider position you are changing the amount of current flowing through the magnatic coil. As you go to either the left or the right end of the slider the magnatic field become weaker as the current decreases.So.
a. There is a position of the battery slider control for which the magnetic field is zero Because when you changes the direction of the current you have to have cross the zero.

b. The field changes direction as you move the control all the way to the left, then all the way to the right. Here basically you reversed the direction of current in the magnatic coil.

c. The field alternately gets weaker, then stronger, then weaker again, then stronger again, as you move the slider back and forth ,This is true because you get a maximum current that will flow in the coil for both the direction. and to change the current you crosses zero so your fiels alternately get changes.

d. The field is weaker when the battery slider control is all the way to the right than it is when the slider is all the way to the left.This point is true because your slider is basically a current direction changer.

f. The field is weaker when the battery slider control is all the way to the left than it is when the slider is all the way to the right.this thing happen due to your slider configuration.

e. There is no change to the field as you change the number of coils.This is false because the magnatic field in the coil depends on the the number of turns present in the coil.As the number of turns increases the magnatic field increases(provided the current remain same.)