Can a 12V ac bulb be used with 12V dc adapter or 12v DC supply?

Answer 1

Answer 1: No.

Answer 2: This depends.

The chances are that an AC adaptor can be substituted by a DC adaptor.

It depends on what item it is powering.

Not many items run directly on AC power. Most items that is shipped with an AC adaptor has got its own internal rectifier in order to make DC from AC.

If you know enough about electricity and electronics to open up and check the item you need to power up, then check if it contain an internal rectifier.

If it does, then it should be no problem.

Some times however, the diodes used for rectifying the voltage are tightly dimensioned. 4 diodes is needed to rectify the power. 4 diodes of 500ma give you a usable current of about 1 Ampere if run with an AC power-source.

If using a DC power-source however, the usable current is halved because only 2 of the 4 diodes will be used.

Some items that use an AC adaptor is some clock-radios or answer-machines with time-telling.

For these items it is likely that they will run fine on an DC adaptor except for the clock.

In Europe, the AC is 50 Hz. In US, this frequency's is 60 Hz.

This frequency is highly accurate and can be used to measure time for a clock.

If using DC, then the clock will not function, but the rest should.

Another issue is voltage...

12 v AC... when rectified and not stabilized, it will make about 16.8 volt.

When powering some item, the voltage will drop, but always stay above 12 volt. Probably more like 14 volt. This depending on current drawn.

If using a 12 v DC power-source, this will after diodes only give about 11.3 volt.

It may still be enough for most appliances though.

If not sure about what I am writing about, then you should find a perfect match AC adaptor to your "thing" and not even test a DC adaptor on it.

IF the question was reverted. "Can I substitute a DC adaptor with an AC adaptor" then in 99.9% of cases this is a big NO.

If putting AC where you should put DC, this will most likely lead to destruction of your item. You will "shortcut" capacitors and transistors. It may also cause fire.