The amount of current in a coil directly relates to magnetic field strength
Moving charges create magnetic fields. Each electron moving in a conductor creates its own magnetic field. As electrons move through the coil of wire, the magnetic field of one electron adds to the field of any others moving in the same direction. The faster a charge moves, the stronger the magnetic field it creates. For this reason alone, a higher current implies an electron is moving faster, and as a result, it would create a stronger magnetic field.
The animation above shows the magnetic field created by a solenoid with a small current from a 3V source. | This animation shows the magnetic field created by the same solenoid with a higher current created by a 6V source. Notice that the magnetic field is shown twice as strong. (twice the number of field lines) Doubling the current doubles the field strength. |
In conclusion, we could say the magnetic field strength of a solenoid is directly related to the current through the coil. |