# Electrical conductivity of magnets

1. Oct 8, 2011

### dibilo

My wife was asking me if magnets are conductors of electricity and I told her magnetite isn't.

Then she asked me if an iron rod, after being magnetized is an electrical conductor. That got me stumped.

I am thinking by right it shouldn't affect the electrical conductivity of the iron rod as the "sea of electrons" shouldn't be affected just because it is magnetized but my wife argued that the current will now follow the magnetic field which will turn the iron rod into an insulator or at least a poorer conductor than before.

Anyone can shed some light here so one of us can earn the bragging rights? Thanks!

2. Oct 8, 2011

### mrspeedybob

You're both right.

Scenario 1.
An Iron bar is magnetized so that 1 end is N and the other end is S, magnetic lines of force run through the bar from 1 end to the other before looping back along the outside.
Now if you run current through the bar from one end to the other parallel to the magnetic force lines the field will have no effect.

Scenario 2
An iron bar is magnetized so that N is on one side of the bar and S is on the opposite side. magnetic lines of force run through the bar from 1 side to the other before looping back along the outside and around the ends. Now if you run current through the bar from one end to the other perpendicular to the magnetic force lines the field will deflect the current towered one side of the bar and away from the other. This has the effect of reducing the cross sectional area of the bar through which electrons can easily flow. Since resistance is inversely proportional to cross sectional area of the conductor the resistance of the bar will increase slightly.

Measuring the difference in resistance between the 2 scenarios would require either an extremely strong magnet, extremely sensitive equipment, or both.