24 Nov
2002
24 Nov
'02
7:50 a.m.
Peter Turnbull wrote:
On Nov 24, 10:14, Dave Woodman wrote:
I did not mean to imply that the current is the same, merely to illustrate
that
the power dissipated is proportional to the square of the current! I therefore
stand by what I wrote, for the purposes that I wrote it only.
Your posting does indeed, better analyse the situation, but I was not
attempting
to do that.
The reason that I felt it necessary to post was the assertion that 'current
always
uses the way of lowest resistance' which would imply that the user could have
only one set of cables - and a real fire would be soon on the cards.
Cheers,
Dave.
Let's try to keep this in accordance with
real physical laws:- the
current flowing in the wires will be inversely proportional to the
resistance since the potential difference across them is the same.
So far, so good...
The physical principle
that causes the problem is that the power dissipated is proportional to
the
*square* of the current. In case of any doubters -
Ohms Law:
I = V/R
=> V=IR
Power dissipated:
P = IV
=> P = I(IR)
So, for example, if one cable/connector pair had twice the resistance of
another, the second would dissipate four times as much power as the
first.
Er, no. The current will NOT be the same in each case. If you're going to
use mathematical equations to argue, use the right ones :-)