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That would be resist O r then ...


"Clifford Heath" <no@spam.please.net> wrote in message 
news:42e47327$0$2519$afc38c87@news.optusnet.com.au...
> 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.