A helicopter moves with a constant velocity v, - 4 m/s from point A to point B during a time interval tas = 10 s. It then accelerates from point B to point C with constant acceleration az =
2m/s2 for a time interval tac = 20 s. The average velocity of this helicopter for the whole trip is
equal to:
A
tas-10
tec-20 s
Q2 = 2m/s2
Di=4 m/s​

12000j is work done

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.