Which material rod is often used to make electromagnets?

(A) Steel

(B) malleable iron

(C) Brass

(D) None of these

Which statement is true of magnets?

a) Earth is an electromagnet

b) Electromagnets are weaker than permanant magnets

c) A magnet always has a north pole, and may or may not also has a south pole

d) A permanent magnet can be turned off.

In any one material, all electromagnetic waves have the same______?

What are electromagnets used for?