Why does a volt-meter not show a reading when connected to the same phase?

[foolios]

When a volt-meter is connected to the same phase. Why doesn't it show a voltage reading?

Thanks in advance for any explanations.

 

[Guest123]

Hi.

Do you mean both probes connected to the same conductor???

If so then there is no PD (potential difference) for the meter to read so it reads as 0.

To get a meter to read it needs a PD i.e a flow and return path, L-N, L1-L2, L-E etc etc.

 

[Des 56]

I suppose if the circuit was under load,then the measurement was taken, and it were accurate enough, it would measure the volt drop of the cable for the distance of the probes,but thats a bit too accurate for our needs

As Lenny said there needs to be a potential difference of phase to phase or neutral/earth

 

[foolios]

So then, when there is a load, there is enough resistance in the circuit to cause the flow to want to go into the meter's less resistance. The reason that the meter won't measure potential difference on the same cable is that there is less resistance on the cable than in the meter, thus the flow bypasses the meter since the wire of the circuit has a less resistive path.

Thanks for the replies.

 

[pushrod]

Think of a voltmeter as something that samples the energy (potential) at two different points and then tells you the difference (potential difference).
If you put the two probes on the same live conductor side by side then no energy has been used between the two points so the voltmeter shows no change ie zero volts, even though both conductors are at 230 V relative to earth.

 

[foolios]

Thanks all