You need to exercise your body in the same what that you are going to use it.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.

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.