elect. polarity

[Frank Thompson]

On a device with male prongs identical and also screw connectors are identical how can a determine polarity?

[RBM]

** You would have to do it visually or by using a continuity tester.

[RBM]

NOT REALLY, IF IT IS A SIMPLE DEVICE ITS POWER CORD MAY JUST LEAD TO AN AC COIL AND THE POLARITY IS UNIMPORTANT.

HE MAY HAVE MISSED SOMETHING....ONE SCREW IS NORMALLY SILVER THE OTHER GOLD , BRASS OR BRONZE.....THE SILVER ONE IS GROUND.

BUT AGAIN, IT DOESNT MATTER: SINCE ANY GOOD TROLL CAN & WILL EVENTUALLY PLUG IT EITHER WAY :-)

PAT ECUM

**The OP didn't ask if it mattered. He asked how you can tell, where the hot leg and the neutral leg go (.)

[Tony Hwang]

Hi, In that case, you don't need to worry. Just plug in.

[Jon Danniken]

If it is DC (or polarized AC), the cord will often have the negative (or neutral) voltage conductor marked in some way. Look for a raised ridge, or a stripe.

Double check it with a voltmeter.

Jon

[dpb]

Or there may be indication on the insulation--lamp cord, for example has ridges on neutral conductor side (iirc that's the orientation otomh w/o looking for confirmation)...

[David Nebenzahl]

On 4/26/2011 2:08 AM Frank Thompson spake thus:

You know, it's really hard to tell just exactly what you're asking, with what little information you've given us.

However, since the replies so far have been much less than helpful, I'll try to help you here.

I ASS-U-ME that you're asking about an AC-powered device, and that by "polarity" you mean "which side of the power line is connected to which side of the device". Correct?

Not sure exactly what you mean by "screw connectors", but let me take another guess and say that you're probably referring to a light fixture of some kind.

Very easy to determine polarity (see above definition) here: take your ohmmeter (DMM set to "resistance" or "ohms"), and see which prong of the plug is connected to which side of the light socket or other part of the circuit. Put one meter probe on each part, and see if you get a low resistance reading. If you do, that indicates continuity (in other words, the one thing is connected to the other thing).

In the case of light sockets, like ordinary Edison screw-base sockets, you can simply probe the plug prongs and the "button" at the center bottom of the socket that contacts the button at the base of the bulb. This is normally the "hot" contact, at least in fixtures which can only be plugged in one way (either with a polarized plug or a 3-prong plug).

Note that this is based on U.S./North American practice. Can't say about that weird Brit/Euro stuff ...

Does that help?

[David Nebenzahl]

On 4/26/2011 12:22 PM David Nebenzahl spake thus:

I should also add that if you have a non-polarized plug with identical prongs, then there is no way you can determine "polarity" (that is, which side of the plugged-in device is "hot" and which side isn't), except by using a voltmeter (AC) to measure between each side of the device and the hot or neutral side of the outlet. If you don't know how to do this, please ask before trying it. Pretty simple, but with the possibility of smoke, fire and shock.

[JIMMIE]

What kind of device? Is it AC, DC , either or other.

Jimmie.

[clare]

And technically, with AC there is NO polarity.

[Uncle Buck]

And technically, with AC, half the time it's positive polarity and half the time it's negative polarity.

[clare]

time it's negative polarity.

Obviously - but no such thing as "positive" or "negative" wires - and for most AC devices, other than for safety reasons related to grounding, there is no difference in operation between one connection direction and the other.

[Robert Green]

the time it's negative polarity.

Even more technically, there are two moments in each cycle where their is no polarity - at the zero crossing. That's where the X-10 home automation signal lives. Sort of. (-:

-- Bobby G.

[Frank Thompson]

both are silver

[Frank Thompson]

I am trying to connect a stepdown (120 to 12 volt) transformer, a timer, and a transceiver for a remote alert device. Instructions call for the three to be hooked up in series.

[bud--]

If the timer and transceiver are on the 12V side of the transformer it doesn't matter.

[dpb]

On 4/26/2011 9:59 PM, The Ghost in The Machine wrote: ...

Your caps lock key appears stuck...

[Ralph Mowery]

In what country is the silver one the ground ? In the US the green is the ground.

[SRN]

Well, actually the silver is the groundED conductor (neutral is slang), and the green is the groundING conductor. The "hot" wire is the ungrounded conductor.

[Ralph Mowery]

After 2008 there is an offical term called the neutral in the NEC.