A few things I have been wondering about

[LeonardS]

from what I understand when live is down to earth there is less resistance then taking the intended path through the return conductor to earth at the head or in the road depending on supply system, so more current is drawn as voltage wont change unless its stepped down or up, but will vary in a AC circuit. so a MCB would trip because of overcurrent. I am wondering why doesnt a mcb trip when you touch a live conductor and you're not electrically common as there is even less resistance to earth hence why you're not electrically common? or why the RCD doesnt trip as there would be a load imbalance?

 

[telectrix]

human body is arround 1kΩ resistance, hence using ohm's law, I=V/R, I = 230/1000 = 0.23A which will not trip MCB but may kill you.

 

[ImpededLoop]

^^^^ A shockingly good explanation!

Equation should read I=V/R incase anyone gets confused.

 

[LeonardS]

Thanks for clearing that up, I had answers from the sparks claiming its not making contact with circuit earth, which didn't make sense to me as neither does a MCB haha,

few other things, I was fault finding with a sparks the other day and the lights where not coming on, we found it was because of a loose neutral connection the voltage displayed was much less then 230V but greater then 0V I'm curious why we picked up voltage as theres no path to earth

second thing is why do you have voltage on a ring circuit with no load for the same reason no path to earth it must be the voltage indicator is making that connection? in which case there must be a resistor in a voltage indicator as the mcb would trip?

 

[telectrix]

^^^^ A shockingly good explanation!

Equation should read I=V/R incase anyone gets confused.

cheers. corrected that. must have held the shift key down too long.

 

[Pete999]

Thanks for clearing that up, I had answers from the sparks claiming its not making contact with circuit earth, which didn't make sense to me as neither does a MCB haha,

few other things, I was fault finding with a sparks the other day and the lights where not coming on, we found it was because of a loose neutral connection the voltage displayed was much less then 230V but greater then 0V I'm curious why we picked up voltage as theres no path to earth

second thing is why do you have voltage on a ring circuit with no load for the same reason no path to earth it must be the voltage indicator is making that connection? in which case there must be a resistor in a voltage indicator as the mcb would trip?

It must be me Leonard, I can't make head nor tail of what you are asking.

 

[Deleted member 26818]

Yes, the tester itself is making the circuit connection between whichever conductors are being tested.
Yes there is resistance in the tester.

 

[telectrix]

if you think of an analogue voltmeter, it requires a specific current to move the needle. the more current, the more the needle moves. now, it only requires a few millivolts to do this, so there will be circuitry in series with the meter movement to drop the bulk of the voltage across it. say for arguments sake, the meter movement reqires 1mA for fsd. then the resistance in series will be as near as dammit 230/0.001 or 230kΩ.

 

[LeonardS]

and the voltage I was getting when the neutral was loose on the lighting circuit? I was getting below 230v an above 0v why was that? no path to earth so no voltage should of been picked up?! I believe I was getting like 12v between live and neutral

 

[Deleted member 26818]

With a loose Neutral, rather than a disconnected Neutral, you would have a high resistance connection.
I believe there is an equation you can use which would enable you to determine just how much resistance the connection had using the supply voltage and the measured voltage.

 

[TJ Anderson]

human body is arround 1kΩ resistance, hence using ohm's law, I=V/R, I = 230/1000 = 0.23A which will not trip MCB but may kill you.

Slightly off topic but this reminds me of a lunch time when were meggering KFC Chicken Wings , Tower Burgers, Hash Browns etc. It was so funny but interesting at the same time!! Chicken Wings (all that grease) have quite a low IR lol

 

[Tidy Max]

human body is arround 1kΩ resistance, hence using ohm's law, I=V/R, I = 230/1000 = 0.23A which will not trip MCB but may kill you.

Not everyones is 1kΩ. The best way to test this is get an apprentice, give him the megger probes so you can measure his resistance, crank it up to 1000 and tell him everything will be fine its all in the name of science.....

zap.

 

[telectrix]

Not everyones is 1kΩ. The best way to test this is get an apprentice, give him the megger probes so you can measure his resistance, crank it up to 1000 and tell him everything will be fine its all in the name of science.....

zap.

but will the bugger keep still long enough for you to get a reading on the meter?

 

[spark 68]

Ha Ha, this reminds me of two apprentices with a lead each from the IR tester having slap fights lol :85:

Both got suspended :biggrin:

 

[shanky887614]

Ha Ha, this reminds me of two apprentices with a lead each from the IR tester having slap fights lol :85:

Both got suspended [emoji3]

i dont know how some didnt get suspended.

running around with a capacitor in a pair of pliers and giving it to people lol

 

[telectrix]

years ago, a regular client's brat was always rooting in my toolbox. i put a couple of charged caps in. soon stopped the little bugger.

 

[sammyshooter]

years ago, a regular client's brat was always rooting in my toolbox. i put a couple of charged caps in. soon stopped the little bugger.

Pure evil genius!

 

[PEG]

I do not advocate the electrocution of minors,of course....but i find if you paint your large,capacitors orange,and write "dynamite" on their side,the little rascals seem drawn to them...:bobby: