According to newton's second law of motion, if we we have a rigid, unchanging mass and we observe it accelerating, what must be happening?
a. a force is being applied to the mass
b. a force was once applied but is now not being applied
c. no force was or is being applied to the mass
d. the mass must be changing

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.

less than one you can't create energy