8

How can I check if there is electricity in a power socket without a tester or any other specialized tools?

Note: The method should not involve the destruction of the socket or my whole power supply!

  • 7
    Due to the danger associated with this question I feel this should be on a Electrical/electrician SE site. – Phlume Dec 10 '14 at 21:10
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    DANGER DANGER!! – Experimental Rocket Feb 22 '17 at 16:27
  • You didn't specify that you want to stay safe. Use your fingers! – Jacob Jones Mar 19 '17 at 4:35
  • @ExperimentalRocket HIGH VOLTAGE!! – colmde Sep 24 at 8:02
  • How high is the voltaqe? There is a huge difference between 110V / 220V and 27000 volts. – virolino Sep 25 at 10:43
44

Plug in a working electrical appliance (like a phone charger) and see if it works.

  • 1
    I can't believe how hard I was thinking for an answer to this question... Then this simple answer popped up. – Luke Dec 9 '14 at 22:14
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    Haha, it works every time. – J. Musser Dec 9 '14 at 22:15
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    Please expand your answer that there might still be dangerous electricity on the socket, even if the appliance does not power up (eg if the neutral is disconnected). Your method is good at finding positives, but can have false negatives. – Silent-Bob Feb 22 '17 at 11:35
  • A bad socket could also have a short that could throw sparks, short the appliance, electrocute you... – Allison C Sep 24 at 14:28
4

There's no completely foolproof way to do this.

You can plug in a lamp or other appliance, but this is prone to false negatives (situations where the appliance won't work, but the outlet still has electricity). The most common situation would be a broken neutral wire (the hot wire is still live, but with nowhere for the electricity to go, the appliance won't work). More dangerously, a mis-wired socket with hot and ground switched won't produce a working appliance, but touching any exposed metal on the appliance can kill you.

If you want a definite answer, you need tools. In terms of increasing effort and accuracy, these are:

  1. A socket tester: plug it in and read the lights. This can detect most common problems, but can't tell the difference between a powered-down socket and a live socket with two broken wires.
  2. A non-contact voltage meter. Touch it to each contact of the socket and see if it beeps. Unlike the other methods, this is prone to false positives, where an induced signal from one wire can cause another wire to be reported as live.
  3. A voltmeter or multimeter. Measure the voltage between each pair of contacts. The hot-neutral and hot-ground voltages should be within 5% of your local line voltage, while the neutral-ground voltage should be close to 0. Unlike the other methods, this is not prone to either false positives or false negatives.
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The hardcore test, still "safe". Only to be used if really needed.

It assumes that the voltage is standard 11V / 220V.

  1. Use an thin wire, properly insulated at one end, NOT insulated at the other. Some screwdriver should do the job just fine.

  2. Be VERY CAREFUL not to touch an metal part of the wire.

  3. Insert the wire into one of the holes of the socket.

  4. DANGEROUS: with the back of your hand "slap" the uninsulated part of the wire, in a way that will not make it possible to leave your hand in contact tot he wire. UNDER NO CIRCUMSTANCE SHOULD YOU TOUCH THE WIRE WITH THE PALM-SIDE OF YOUR HAND. THERE IS A RISK THAT YOUR HAND WILL CLENCH ON THE WIRE AND THAT WILL BE YOUR END.

  5. DANGEROUS: If there is no shock, try again for a few times, very slightly extending the time of contact. If there is still no shock in the hand, the "hole" is not electrified.

  6. Repeat 3-5 for the other hole.

It will work better if you wash your hands first, removing the excess water with a towel - espeially if your hands are usually very dry.

  • This is "safe" in the sense that there's only a low probability of being killed by it. You're counting on involuntary muscle contractions or the momentum of your hand to break the circuit before the shock kills you. – Mark Sep 25 at 22:08
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    @Mark: agree, that is why I added all the warnings. Actually, that is the method to test a stray wire (maybe on the street) if it is electrified, without proper tools. I just adapted it for testing the socket. – virolino Sep 26 at 5:22
  • A "stray wire on the street" could very well be a distribution line rather than a service drop, in which case it carries enough voltage to kill you with even a brief touch. (Ironically, power companies call this "low voltage", despite it being in the 2-50 kilovolt range.) – Mark Sep 27 at 20:33

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