using a multimeter

[ste v]

WHY DOES THE VOLTAGE ONLY SHOW WHEN THE EARTH LEAD IS CONNECTED TO EARTH ?

[scotman]

I don't understand what you mean about a multimeter with an earth lead. What make and model of meter is it?

[ste v]

it's an old analogue meter with a needle not a digital screen called an sa9083

[ChuckFickens]

I think they are getting confused between earth and negative.

Voltage is by it's very definition the potential difference between TWO points across a circuit, volts can not just flow into anything without leaving again (hence why birds can sit on high voltage cables and not get electrocuted)

[4candles]

The SA9083 is, or certainly was, a BT linesman's tester - standard issue.

There are three connections: A-wire, B-wire, and earth.

All connections are attached to the line in question, then a rotary switch is turned to test for various conditions on the line.

Operating manual here - http://www.jmwlimited..._Operating_Manual.pdf

[buildersmate]

Yes, but how does that answer change the price of fish?

[4candles]

The higher the fewer - obviously.

[buildersmate]

Ah yes, the higher obscurity of the answer the fewer the number of people able to comprehend.

[annieigma]

Hi,
Yes the 9083 is a BT engineers test instrument. All test meters will show voltage if one wire is connected to the earth by putting the clip into the wet soil or something that is connected to the earth/ soil.such as a water pipe, radiator etc. and the other lead to a wire,such as live mains 250v AC, a phone circuit, 50v DC This is because all transformers that produce electricity are centre tapped to earth, which means the neutral wire in any electric circuit is basically an earth wire. For instance, you can can get a telephone with batteries in ( field phone) and put one lead on a live telephone wire and the other in some outdoor wet soil and get a dial tone. not very good transmission, but it works. The railways actually used a one wire and earth system for their phones until a few years ago. This is all to do with the magnetic field of planet Earth and the fact that wet soil and natural minerals in the soil are conductors. I was told this at C&G classes, so should be correct.