AC Current direction

[dhanasingaraja]

Hello genius,
Ac current is alternate in direction.but if i check the terminals (at residential single phase supply) with tester,phase indicates voltage but neutral not. Why ?

 

[chuckey]

the tester measures the voltage between its contact and its capacity to earth. So high voltage, loads of current to earth, LED lights. Neutral, no voltage to earth, no current , LED no light.
Frank

 

[Tahmid]

Neutral and earth are at the same potential. So, LED does not light as there is no potential difference. Live varies from +220V to -220V (with reference to neutral) and so lights LED due to the potential difference.

 

[dhanasingaraja]

for AC ,current direction is alternative. so,for the first half cycle current direction should be phase to neutral and for the next half should be neutral to phase.so power should present on both terminals alternatively.I can see this in attached proteus simulation.but not in real time.why it is?

 

[Tahmid]

Neutral is always at a potential of zero. In the first half cycle, live is positive (up to +311V with respect to neutral). So, current flows from live to neutral. In second half cycle, netral is still zero, but live is negative (down to -311V with respect to neutral). As neutral is at a higher potential than live, current flows from neutral to live.

 

[dhanasingaraja]

In the simulation i can't see zero potential at anywhere.voltmeter shows potential on both terminals alternatively.then how to say which one is phase and neutral?

 

[Tahmid]

From the simulation, you can't deduce potential. You can deduce potential difference. It is due to the potential difference that neutral is alternately positive and negative. If you test the neutral with tester, light doesn't glow, because it is at the same potential as the earth.

 

[peeyushsigma]

neutral wire provides only reference ...your body and the earth or neutral have same potential so when you connect the tester to the neutral wire then no current flows through the tester ...but when you connect with live wire the current flows via tester and body that completes the circuit and led glows...

 

[tahir4awan]

This question also confused me and also I asked the same question and it took time to understand. Neutral wire always remain at 0 potential and live wire always have potential. Now question arise about direction. You can understand it in a simple way.The supply will push electrons in first have cycle and in negative half cycle the supply will pull electrons.Note that live wire will remain at some potential but reverses its direction due to supply pushing and pulling.