Since the magnetic field is proportional to the product "NI", the number of turns in the windings "N" and the current "I" can be chosen to minimize heat losses, as long as their product is constant. Since the power dissipation, "P = I2R", increases with the square of the current but only increases approximately linearly with the number of windings, the power lost in the windings can be minimized by reducing "I" and increasing the number of turns "N" proportionally, or using thicker wire to reduce the resistance. For example, halving "I" and doubling "N" halves the power loss, as does doubling the area of the wire. In either case, increasing the amount of wire reduces the ohmic losses. For this reason, electromagnets often have a significant thickness of windings.