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.

Hi Rumble

I was hoping to measure the resistence across the live/neutral pins
of the mains plug and then deduct the resistence of the main lead
(which is approx 10m of 1.0 mm^2).

From the result I was looking to know what the cold bulb resistence
is and from that infer the wattage.

The idea is to save opening up the housing and taking the bulb out to
measure the resistence.

Your table is useful and I have kept it but it does not directly
address my problem unless I do your calculations below each time.

Can I find a simple table which gives me resistence per metre of 1.0
mm^2 wire (or whatever cable I am using)?


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. :-)


--