Question for all you EEs.

[lionkingcmsl]

You have two relays: one is rated 12VDC, 1000 ohms, the other 24VDC, 1000 ohms.

My question is: What determines the voltage of the relay? Also, how does one make a DC relay versus an AC relay. I know you can use DC on an AC relay, but not the other way around.

I know it has to do with the windings, but I can't figure out how.

Comments

[shockwave77598.livejournal.com]

A certain amount of current has to flow through the coil to pull the armature. They make the coils for higher voltage relays finer so they have higher resistances. Ah, but they also use fewer turns, which lowers the resistance right back down again. The current through the 24V relay would be double, but fewer winding would mean less magnetic field is created than the 12V one. So when enough magnetic flux is created, the contact moves. Less flux is made in the 24V relay coil as the winding is finer but there are fewer windings.