An object falls from a height of 12m. The object's potential energy at the top is 50J. Where is the potential energy of the object 25J

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.