<span>The larger the current flowing in a wire, the stronger the magnetic field is that surrounds the wire.
That's why, if you want to make an electromagnet stronger, one way to do it is to add another battery. By increasing the voltage, you'll increase the current flowing in the coils of wire, and the electromagnet will be stronger.</span>
The magnetic field strength due to a current carrying wire is directly proportional to the amount of current flowing through the conductor and the length of the conductor. By the Biot Savart's law, the amount of magnetic field strength produced due to a small length element is given by
dB = k dl x i / r^2
Where, dl is the small length element, i be the current and r be the distance from the conductor where the magnetic field strength is to be calculated.
