No Attempt 50% Part (a) If one of the charge's magnitude is increased by a factor of 4 and the distance between the charges is increased by a factor of 7, what will be the new magnitude of the force exerted by one charge on the other (as a multiple of F)?

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.