Question

how will you prove a solenoid

Answer 1

A solenoid is a coil of wire designed to create a strong magnetic field inside the coil. By wrapping the same wire many times around a cylinder, the magnetic field due to the wires can become quite strong. The number of turns N refers to the number of loops the solenoid has. More loops will bring about a stronger magnetic field. The formula for the field inside the solenoid is

B = m0 I N / L

This formula can be accepted on faith; or it can be derived using Ampere's law as follows. Look at a cross section of the solenoid.