Question

the resistance of a coil for direct current is 100 ,but when alternating current is send through it, now its resistance will be?

Answer 1

Thank you for asking this question.  A really easy but an interesting question to ask. 
Now its resistance will be around 160. This is because AC current has 1.6 times more resistance through the same conductor than DC current. The AC resistance is more because of the fact it exhibits skin effect when  AC current is passed through a conductor. 
I hope this answer can help you in some manner.