Fundamental quantities

The quantities which do not depend on other quantities is called fundamental qiantity. For eg; time,current,lwngth etc...

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.

double the distance = divide strength by 4