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With an electromagnet, if there's a open reed switch betwen 1 end of the coil's wire & powersource, will e-mag get hot? Answered

I'm building an electromagnet.
The core is soft iron: 0.5" diameter and 1" long.  AWG 12 wire OR enameled copper magnet wire 32 gauge

So the wire is wrapped around the core. One wire end leads to a reed switch which connects to one of the two wires of the 9 volt snap-on battery clip. The other wire end connects straight to the 9 volt snap-on battery clip with nothing in between. Will the wire end that connects directly to the 9 volt snap-on battery clip:
A.) use powers and drain the battery
B.) heat up the electromagnet (wire & core)

If the electromagnet heats up, then how hot does it get? Just warm or really warm? Could it reach hot or HOT levels - hot enough to burn skin, damage any part of the electromagnet, or ignite/melt the carpet (if it was on it)?

P.S.  The final device would have no exposed wires.


3 Replies

NachoMahma (author)2010-02-01

.  No current will flow through the circuit until the reed switch is made/on/1. A break in a series circuit stops current everywhere in the circuit.
.  How hot it will get depends on what gauge wire you are using, how long the wire is, and how much current a 9V battery will put out.

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frollard (author)NachoMahma2010-02-02

That pretty much covers it:  good ol ohm's law V=IR and P=IV or P=I2R
Measure the resistance of the circuit in ohms, and solve for I

Say it has 0.5 ohms resistance (guess) 9=I(.5), solve for I = 18 amps.  I don't think a 9volt battery can put out 18 amps, but it will put out a fair amount...

P=IV, 9Vx18A = 162 watts...probably can't run a 9v at that power...but if you do, it will get HOT.

Traditionally I know you can put 2x 9v batteries together as a makeshift hand warmer (bad idea).  They get quite warm...

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I once fell asleep on the couch with a couple of 9v batts and a couple handfuls of loose change in my pocket. Wouldn't recommend it....

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