Inductors And Dc:

Assume that you have some wire which conducts electricity very well. When you wind a length of the wire into a coil and join it to a source of dc, the wire draws a little amount of current at first, but the current rapidly becomes very large, probably blowing a fuse or over-stressing a battery. It does not matter whether wire is a single-turn loop, lying randomly on the floor, or wrapped about a stick. The current is large. In amperes, it is equivalent to I = E/R, here I is the current, R is the resistance, E is the dc voltage, and of the wire (i.e., a low resistance).

You can might an electromagnet by passing dc via a coil wound around an iron rod. Though, there is still a large, steady current in the coil. In a practical electromagnet, the coil heats up as energy is degenerate in the resistance of the wire; not all the electrical energy goes into the magnetic field. When the voltage of the battery or power supply is raised, the wire in the coil, iron core or not, gets hotter. Eventually, when the supply can deliver the essential current, the wire will melt.