Question

The image shows copper wire coiled around an iron nail and connected to a battery to create an electromagnet. http://static.k12.com/calms_media/media/1145500_1146000/1145790/1/c8b0d168aef610f65af455737091ea78749d8482/MS2_PHY_08_13_assess_07_electromag.jpg

How can the magnetic field of this electromagnet be increased?

A. Decrease the number of coils around the nail.

B. Increase the number of coils around the nail.

C. Shorten the length of wire between the battery and the nail.

D. Replace the nail with a plastic tube

I'm pretty sure its not D but that's all I know XD

Answer 1

exactly, using plastic will just make the field weaker.
the lenght of the wire between de battery and the nail has nothing to do, it wont change anything.
If we increase the number of coils around the nail we will get more current per lenght unit, and since the field for this kind of arrangement is proportional to that magnitude, it will be increased!
so B is the answer here.

Answer 2

Ok thankyou! That makes sense :D

Answer 3

One more thing, were is the strongest point on a horse shoe magnet? If you know XD

Answer 4

i think it should be right in the surface of the endings

Answer 5

Yeah thats what i was thinking.. Thanks!

Answer 6

np!