Use the letters to mark the centimeters and millimeters on the ruler. The first one (A) was already done

answer; equivalent to a one(1) horsepower motor;

at right angles to each other

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.