[Elecraft] Elecraft Digest, Vol 114, Issue 11

[David Cutter]

So far nobody has mentioned insulation material.  The rating of a cable has 
little to do with melting the wire and mostly to do with melting or 
softening the insulation which would create a shock and/ or fire hazard. 
The same size wire insulated with PVC is allowed to rise to a much lower 
temperature compared to insulation of PTFE or numerous other materials.  And 
what is good or bad for mains circuits will not be the same in a vehicle or 
aircraft circuit.

David
G3UNA




----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at embarqmail.com>
To: <elecraft at mailman.qth.net>
Sent: Monday, October 07, 2013 11:14 PM
Subject: Re: [Elecraft] Elecraft Digest, Vol 114, Issue 11


> OK Joe,  You are correct.  It has been a very long time since I have been 
> involved with heat related science issues.  More current equals more heat 
> (for a given resistance) has been sufficient for me most of the time 
> without getting into the exact math.
>
> It is good to know that some folks here still have those formulas on the 
> top of their heads.
>
> 73,
> Don W3FPR
>
> On 10/7/2013 5:57 PM, Joe Subich, W4TV wrote:
>>
>> On 10/7/2013 5:31 PM, Don Wilhelm wrote:
>> > Geesh, how is that possible - twice the current equals twice as much
>> > heat and will exceed the capacity of the wire.
>>
>> Sorry, Don ... twice the current => *four times* the heat. Heat
>> (energy in Joules) = Watts * seconds.  One Joule (one Watt-second)
>> is 2.78e-7 kW*h
>>
>> 73,
>>
>>    ... Joe, W4TV
>
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