If the coils of an electromagnet are placed inside a set of secondary coils, what has to happen to create a current in the secondary coils? a.
The current in the electromagnet must be zero.

b.
The current in the electromagnet must be constant (but not zero).

c.
The current in the electromagnet must be constant (or zero).

d.
The current in the electromagnetic must be increasing or decreasing - changing and not steady.

there are no contact forces mentioned on the list of choices that you've provided.

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.

no. bullets are macro objects. wave nature is for light waves, extremely tiny particles. if a light particle was the size of your finger, the bullet would be the size of the universe. so basically, that huge difference in size makes the wave nature of matter insignificant.