What is the highest and lowest frequency a human being can hear

Every person is different.  But for a planet-wide overall average that roughly represents all human beings on Earth, the figures usually used are:

from  20 Hz  to  20,000 Hz .

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.