By how much does the gravitational potential energy of a 54-kg pole vaulter change if her center of mass rises 4.0m during the jump?

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.

365.25 earth days are in the year of a light year