Here's a question to all you bright sparks out there. I've made it up so you won't find the question or answer on google.
An unknown length of cable has all conductors with csa of 2.5mm. The circuit is extended with an unknown length of cable with Live conductors of 2.5mm and CPC of 1.5mm.
You conduct a resistance test on the TOTAL circuit:
R1+R2 = 0.4
R1+Rn = 0.3
1. Tell me the length of the original cable before you extended the circuit.
2. Tell me the length of new cabel added to the original circuit.
[PS - Imagine going through life not knowing what Rn is - people call you ignorant, stupid, a fool, dangerous - you looked high and low, trying to ascertain what this marvellous beast Rn was. You already knew what R1 and R2 was - and even though you thought them pathetic names (you thought RL and RE would be better) - you went with it, but then suddenly Rn came out of the closet ... hmm R1, R2, surely R3? No, there was no R3 (perhaps this will be disovered later) R1, R2, and ... ahem Rn - this really must be something fantastic. When the rain came out, you'd try to walk to the end of the rainbow to find this super Rn - sparkies were talking about it in pubs - it must be something magical you'd think ... months passed, but this mysterious Rn was still unknown ... You couldn't wait for the day to find out what this Rn was - bright sparks were laughing at you all the time, pushing, prodding, "ha ha, you don't know what Rn is, lah de dah de dah dah" ... "you're dangerous, you're stupid". So a determined search for this marvellous Rn must happen ... a further few month's passed, then I passed a bright spark testing at the CU ... I could just hear him from outside the window ... "we've done the R1, R2 test", he said to his mate ... "now take the croc clip off the Earth and whack it on the neutral and we'll do an R1, Rn" ... WHAT ... I fell down in tears, my eyes were protruding with rage, .... IS THAT IT? Really. So there was no magic, no marvellous thing - it was just a term used by sparkies for a very simple thing, so it could be used, like a language to maintain a distance from normal folk - just like PFC, Zs, Ze - and all the other terms used - they seem mystical and magical, but they are not. Not knowing them doesn't make you dangerous - not being able to calculate a length of cable might]
Use this data for your calculation
1.5mm = 12.1
2.5mm = 7.41
That should be all you need - Anyone?
An unknown length of cable has all conductors with csa of 2.5mm. The circuit is extended with an unknown length of cable with Live conductors of 2.5mm and CPC of 1.5mm.
You conduct a resistance test on the TOTAL circuit:
R1+R2 = 0.4
R1+Rn = 0.3
1. Tell me the length of the original cable before you extended the circuit.
2. Tell me the length of new cabel added to the original circuit.
[PS - Imagine going through life not knowing what Rn is - people call you ignorant, stupid, a fool, dangerous - you looked high and low, trying to ascertain what this marvellous beast Rn was. You already knew what R1 and R2 was - and even though you thought them pathetic names (you thought RL and RE would be better) - you went with it, but then suddenly Rn came out of the closet ... hmm R1, R2, surely R3? No, there was no R3 (perhaps this will be disovered later) R1, R2, and ... ahem Rn - this really must be something fantastic. When the rain came out, you'd try to walk to the end of the rainbow to find this super Rn - sparkies were talking about it in pubs - it must be something magical you'd think ... months passed, but this mysterious Rn was still unknown ... You couldn't wait for the day to find out what this Rn was - bright sparks were laughing at you all the time, pushing, prodding, "ha ha, you don't know what Rn is, lah de dah de dah dah" ... "you're dangerous, you're stupid". So a determined search for this marvellous Rn must happen ... a further few month's passed, then I passed a bright spark testing at the CU ... I could just hear him from outside the window ... "we've done the R1, R2 test", he said to his mate ... "now take the croc clip off the Earth and whack it on the neutral and we'll do an R1, Rn" ... WHAT ... I fell down in tears, my eyes were protruding with rage, .... IS THAT IT? Really. So there was no magic, no marvellous thing - it was just a term used by sparkies for a very simple thing, so it could be used, like a language to maintain a distance from normal folk - just like PFC, Zs, Ze - and all the other terms used - they seem mystical and magical, but they are not. Not knowing them doesn't make you dangerous - not being able to calculate a length of cable might]
Use this data for your calculation
1.5mm = 12.1
2.5mm = 7.41
That should be all you need - Anyone?
