the entrance to a private car is protected by a boom which closes the entrance. the boom can be made to balance by fixing the counterweight a short distance(0.5m) from the pivot on thr main support. if the weight of the boom alone, f, is 400n acts 3.0m from the pilot as shown, calculate counter weight required for the boom to be balanced

positive reinforcement? ?

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.