Two technicians are discussing magnetic coils. technician a says that the magnetic force can be increased by increasing the number of windings in the coil. technician b says that won't because adding windings also increases the length of the wire, so current flow will go down and the magnetic strength will be the same. who is correct.

The magnetic field of a coil is given by

where  is the magnetic permeability,  is the number of windings,  is the current in the coil,  is the length of the coil.
Thus if we increase the number of windings we increase the coil magnetic filed. Technician a) is right.
It is true that increasing the number of windings will increase the length of the wire but the equivalent decrease in the intensity of the current (given by this) is not significative when compared with the increase given by increasing the number of windings.  

Ithink your answer is d

The answer is a.  i hope this