[Duo2400] Re: 2400 fuse

[Stephen]

Roger. Voltage drop. Sorry, misunderstood.

Stephen

>I think I wasn't making myself clear here.  The voltage I was referring
>to was the voltage across the fuse itself (i.e. the differential voltage
>between one end and the other).  This is a function of the internal
>resistance of the fuse compared with the resistance of the rest of the
>circuit, and the voltage across the whole circuit.
>
>If (say) the fuse has a 1 ohm internal resistance and the rest of the
>circuit has a 99 ohm resistance, the total being 100 ohms, then 100
>volts applied across the circuit produces a current of 1 amp through the
>whole circuit, including the fuse.  But the fuse has a resistance of 1
>ohm and is carrying 1 amp, so the voltage across the fuse (between one
>end and the other) is 1 volt.  So should this fuse therefore be rated at
>1 volt or 100 volts? Does it matter?!
>
>The current rating of a fuse depends on its internal resistance and the
>difference in voltage at its two ends. These are what determine both the
>current it is passing (V/R), and the power it is dissipating (V^2/R or
>VI).  But the 'V' in these expressions is the voltage across the fuse
>rather than the voltage in the rest of the circuit.
>
>Cheers,
>
>Andy
>
>
>---------------------------------------
>Andy Nicholl
>Dunfermline, Scotland
>Fax 0870 130 4955
>email andynic at bigfoot.com
>----------------------------------------
>
>
>
>-----Original Message-----
>From: Duo/2400 List [mailto:DuoList at lists.themacintoshguy.com] On Behalf
>Of Stephen
>Sent: 07 January 2004 18:25
>To: Duo/2400 List
>Subject: [Duo2400] Re: 2400 fuse
>
>
>??? The voltage rating of a fuse is VERY important. I don't know how
>much damaged Marine electronic gear I've seen over the years where
>someone used a 120v fuse instead of a 12v fuse of the same amperage. P =
>VI, power equals volts times amps.
>
>Stephen
>
>>Hi!
>>
>>There would not normally be a voltage rating for a fuse, because they
>>work on the amount of current passed, not the voltage.  5 amps at 1
>>volt is the same as 5 amps at 110 volts as far as a fuse is concerned.
>
>>A fuse has a very low resistance, and works (blows) only on the basis
>>of the differential voltage between the two ends, not the absolute
>>voltage. I=V/R if I remember correctly.
>>
>>There may of course be other considerations, such as size or rate of
>>blow, but a voltage rating will normally only refer to the amount of
>>insulation in the construction of the fuse, etc., which prevents arcing
>
>>over to other nearby components.
>>
>
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