Looking at the position of the house and the tree, if the man ran starting from the house going to
the tree in 8 seconds, the average velocity would be?

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.