You are given a sufficiently long piece of thread, a meter stick and a thin round shape iron rod. Explain how would you measure the diameter of iron rod by using given thread and meter stick.
This length = n x 2πr, where n is the no. of windings and r is the radius of the rod.
Therefore, the diameter of the rod = 2r = The length of wire used for ‘n’ windings /nπ