A circular flat coil that has N turns, encloses an area A, and carries a current i has its central axis parallel to a uniform magnetic field B in which it is immersed.
The net torque on the coil is .

a) iBA
b) NiA
c) NiB
d) NiAB
e) Zero

Sublimation- which change of state is shown in model

Ke reqd to move from 0 to 50 will be proportional to 50x50 or 2500. this is equal to w.  to change vel from 50 to 150 you need energy prop to 22500 - 2500 = 20,000. this corresponds to 8w.  best answer is a) . work reqd is prop to velocity squared.