If one assume that each turn is like a strand of electromagnet, which can then be added up. Therefore, increase in the number of turns will yield to increase in the magnetic strength. Also if the current increases, then there will be increase in the magnetic field strength.
From Ohm's law
V = IR
I = V/R
That is a direct increase in voltage will lead to increase in current.
Increase the voltage of the battery and increases the number of turns of the coil. Will suit the situation
