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Strange observation


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I found an DC adapter designed to give 12V output. When i checked the output by a multimeter the reading was 23V approx.

I switched it off but the multimeter still maintained that reading and then the value started to decrease slowly.

On this, i shorted the capacitor in it (1000microfarad/25V) so the reading becomes zero.

I switched on the adapter again and the reading again reached 23V.

Something is wrong in the capacitor, but how is it happening. I have never read anywhere about anything like this.

The multimeter is fine.

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Hi Siddharth,

This is completely normal for this kind of DC adaptor. It can be fatal to any low current 12V circuit so be careful when using it for anything other than what it is designed for. Whatever it is designed for can be equipped with a built in regulator and is then safe. There is some kind of marking on it telling you how much current it

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Check these out:


Regarding the slow decrease of the voltage when you unplug the adaptor, it is absolutely normal. It is a simple discharging RL circuit; L because the transformer of your adaptor has an inductor and R because voltmeters have big resistances.

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