Question

A student connects a long air-cored coil of manganin wire to a 100-V d.c. source and records a current of 1.5 A. When the same coil is connected across 100 V-50 Hz a.c. source, the current reduces to 1.0 A. Why ? Calculate the reactance of the coil.

Answer 1

 For DC , we have i_dc = V/R  ...(i)

While in A , we have i_rms 

Where XL is the reactance of the coil . Here V = 100 V and also V_rms = 100V

∴ i_rms  = i_dc