�
From equation ( 12 ) peak value of current in the coil is
i 0 = V 0 / ωL or V 0 =( ωL ) i 0
Comparing it with the ohm ' s law we find product ωL has dimension of resistance and it can be represented by
X L = ωL
� where X L is known as reactance of the coil which represents the effective opposition of the coil to the flow of alternating current X L = ωL is zero for DC for which ω = 0 and increases as the frequency of current increases
AC through pure capacitor
�
Figure given below shows circuit containing alternating voltage source V = V 0 sinωt connected to a capacitor of capacitance C
� �
Suppose at any time t , q be the charge on the capacitor and i be the current in the circuit Since there is no resistance in the circuit , so the instantaneous potential drop q / C across the capacitor must be equal to applied alternating voltage so q / C = V 0 sinωt