Electrical apprentice, need help understanding some electrical principles.

I'm struggling with my assessment, so if I ask you guys on here would you be able to explain to me the answer and why it is that?

The ones I'm stuck on are..

A coil is connected to a 100v d.c. supply and takes a current of 10amps, what is the resistance of the coil? If I understood it rightly the answer should be 10 ohms?

The same coil is then connected to an a.c. supply of 100v (rms) and the current is found to be 6a. Explain why the a.c. current is smaller than DC current, by referring to the relationship between resistance, inductance and impedance?

If the supply voltage is 100v a.c. with a period of 20ms and the supply current taken at the coil is 6A calculate the (i) frequency of the supply (ii) overall impedance (iii) inductive reactance (iv) inductance of the coil

Calculate the power factor and phase angle of the coil