how does ohms law apply in power system
Somehow you are confused, but the principle of ohms law is very simple and still valid. 

The resistance of a thinner wire is larger than that of a thick wire, so the current trough the 100W bulb will be larger than the current trough the 60W bulb. 

Furthermore the (tungsten) wires of a light bulb are coiled, to have them evaporate at a slower rate. This can be seen in this picture from wikipedia:



Therefore it's hard to say something about the length. The lenght might appear shorter, but can still have more turns in the coil.