one for the electricians

[mitzimad]

is there a way to tell which direction electricity is flowing through a wire?

 

[Yorick]

From my A'Level physics it, it doesn't actually move. The electrons or whatever, just vibrate. Or something.

Yes, I have been to the pub

 

[Richard n Ann]

Interesting question. Why are you asking ??

 

[tonyidle]

Convention uses positive to negative. In reality it's from negative to positive.

 

[peterc10]

is there a way to tell which direction electricity is flowing through a wire?

AC or DC current?

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[autorouter]

If you can disconnect the wire, you can use a multimeter set to amps. Connect the red and black test leads between the wire end and whatever it was connected to. The meter becomes part of the circuit, and the current flows through it. You need to set the appropriate range: 2A, 20A, 200A etc. You may need to plug the test lead into a special socket on the meter (not the one used for voltage measurements).

If the reading is positive, the current is flowing into the red lead and out of the black lead. If the reading is negative, it is the opposite.

If you can't disconnect the wire, or don't want to, then you can use a clamp meter that clamps round the wire without disconnecting it. Reversing the clamp meter will give the opposite reading. The direction is sometimes marked on the clamp. But best to double-check by doing a simple test on a known supply, such as the positive terminal of a car battery. You know current flows out of the positive terminal.

Convention uses positive to negative. In reality it's from negative to positive.

The direction of flow was chosen arbitrarily before the nature of electricity and the characteristics of the charge carriers was known. It was a 50/50 guess, but unfortunately it was wrong. Charge carriers in metals are negative, and flow from negative to positive. But to this day, engineers and scientists still always describe current flow as moving from positive to negative.

 

[Silver-Fox]

is there a way to tell which direction electricity is flowing through a wire?

Yes it’s like water in a pipe.
It will take its easiest path and normally down hill ??

 

[DBK]

To detect the direction the current is flowing you will have to use a multimeter as an ammeter as described above. Current can flow in both directions into the positive terminal of a battery depending on whether it is being charged or discharged. Think of it like water in a tap - when you open the tap water flows out (discharge) but if you blow hard enough you can force the water back in just like charging a battery.

 

[mark49]

Cut the wire, then see which one has power to it then that’s the way it’s coming.Then connector block the wire.

 

[mitzimad]

To detect the direction the current is flowing you will have to use a multimeter as an ammeter as described above. Current can flow in both directions into the positive terminal of a battery depending on whether it is being charged or discharged. Think of it like water in a tap - when you open the tap water flows out (discharge) but if you blow hard enough you can force the water back in just like charging a battery.

as a plumber by trade i think of all electricity as flow and return

Cut the wire, then see which one has power to it then that’s the way it’s coming.Then connector block the wire.

not if there is a battery either end is a b2b wire

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[mitzimad]

maybe i should elaberate i inherited a b2b charger i spoke to sterling and wired it upo and it showed 10 amps discharge on my screen in the van spoke to sterling again and got the opposite advice re wiring so i reversed it and then it showed 6 amps of discharge so i dissed it and forgot about it with winter coming im thinking of reconnecting
i handt thought that an ampmeter will show positive or minus so will try that

 

[csd4t]

It's all done with those little electrons they hide in the wires all the time only moving to their neighbours when told

 

[icantremember]

I think you can use a compass on the cable but don't know the details.

 

[Lenny HB]

Convention uses positive to negative. In reality it's from negative to positive.

And that is why measuring with a multimeter/ampmeter will give you the wrong answer as they are set up for convention not to give you the truth.

 

[eddie]

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[mark49]

wire

Which would mean it’s coming 2 ways.

 

[DBK]

maybe i should elaberate i inherited a b2b charger i spoke to sterling and wired it upo and it showed 10 amps discharge on my screen in the van spoke to sterling again and got the opposite advice re wiring so i reversed it and then it showed 6 amps of discharge so i dissed it and forgot about it with winter coming im thinking of reconnecting
i handt thought that an ampmeter will show positive or minus so will try that

If you wire up the B2B exactly as Sterling recommend with the cables going to the battery terminals any on board battery monitor you have will not show the true charging current.

Assuming you have a shunt doing the current monitoring then the cable from the vehicle battery negative should not go to the hab battery negative directly, as Sterling say it should, but to the shunt terminal which is furtherest away from the batteries, so to speak. What I mean is the shunt has two terminals, one connected to the battery and one to all the returns from the load. It is this second terminal you need to link to the cab battery negative to. You should also connect the common return to the B2B here although you could connect it to the veh battery negative. If you do it this way all the charging current flowing through the leisure batteries has to pass through the shunt and will thus be measured.
It took me a while to work out what happens when a B2B operates as it isn't obvious, or it wasn't to me! Current flows into the B2B from the cab positive then flows out again to the leisure positive. If you connect the leisure negative to the cab negative the current completes the loop through this cable. Very little current flows in the common negative back to the B2B, the function of this cable is mostly to provide the potential for the electonics in the B2B to work.
Sterling could improve their product if they included instructions on how to install it in MHs as they don't cover any of the above or explain why any split charge system needs to be disconnected.

 

[autorouter]

A B2B is definitely one situation where current could flow either way, if there is a fault for example. I'd prefer to use a clamp meter, because connecting in a standard ammeter might well disturb the circuit and show misleading results, unless you get everything correct and make good solid contacts.

The current should flow from starter battery (actually from the alternator) towards the leisure battery when the engine is running. When the engine stops there should be no flow at all, in either direction. Ignore the flow through the third wire, it's not relevant.