Some one help me this is related to me last question

wavelegth as in spectrum red oygbiv

you can cut your hand off if your not

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.