JS said the following on 07/12/2005 14:08:
Google has not been my friend lately. Seems simple but I can't
locate some electrical data.

Where on Google can I find a simple table showing the typical
resistence per metre of mains flex with copper conductors and
different cross-sectional areas (0.5 mm^2, 0.75 mm^2, etc)?
Measured at room temperature.

he http://www.batt.co.uk/images/pics/31874H3A.pdf

Would *tinned* copper conductors
make a a noticeable difference to the resistivity?

Tinned copper will not materially affect the resistance (not resistivity
- wrong word in this context).


I am in ther UK. If I measure the resistence of 10 metres of
mains flex with my DC ohm-meter then will my resistence reading be
noticeably different to the resistence when I actually make use of
the 10 metre flex to light a 500W floodlight powered from the AC
mains at 230 volts/50 Hz?

No.


Table 4H3B gives the volt drop of the cable in mV/A/m. You should allow
for a maximum of 2% drop in voltage at the far end of your flex.

I'm not sure *why* you would want to know the resistance per se, but you
can work out the resistance from these figures.

So,

Assume your voltage is 240V A.C. 2% volt drop is 0.02 * 240 = 4.8V

The current through your halogen lamp is I=P/V = 500/240 = 2.08A

If you used 1mm sq flex, the volt drop would be 46mV/A/m

So the volt drop in this example would be 46mV * 2.08 * 10 = 0.95V which
is well under 4.8V. :-)

HTH