If the linear dimensions of the core of a cylindrical coil are doubled keeping the number of turns per unit length constant, the inductance of the coil will be (assuming complete winding over the core)
doubled
four fold
eight times
remains unchanged
The inductance of a coil is given as where N = total number of turns of the coil; A = area of cross section of the coil
; r = radius of the core of the coil,
= length of the coil. If
is doubled the total number of turns will be doubled