That would be resist O r then ...


"Clifford Heath" wrote in message
...
alitonto wrote:
Just a quick question.
Please I need clarification on this:
Would a voltage of say 12volts running through a coil of 10 uh be lower
after the coil?.
Does a coil infact drop the voltage?

Every coil has a resistance, which is what drops the voltage.
You can measure that with a DC meter and work out the drop.

Apart from that, the output voltage will change whenever the
current changes, so that for example, when you first connect
the coil to a resistive load, the current is zero and the
voltage on the resister is zero - all the 12V is across the
coil. The current (and hence voltage on the resister) climbs
as the magnetic field increases. The bigger the coil, or the
smaller the resister, the slower the increase (and the slower
the switch-on). So we talk about the "L/R" time constant.

When you remove the resister, the voltage might well jump to
hundreds or thousands of volts, whatever it takes just so the
current doesn't have to change instantaneously. The energy in
this pulse comes from the stored energy in the magnetic field,
and is what destroys badly-designed switching circuits. It's
also what drives your car's spark plugs.

Clifford Heath.