The law of conservation of energy applies:
a. whenever pe = 0.
b. in isolated systems.
c. in all systems
d. only in open mechanical systems.

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.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it