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I have a piece of kit which requires the following psu, 9v DC 200mA to power it. I have a 9v DC 300mA and was wondering if this would be ok to use, or could it damage the unit? Sorry if it sounds silly (it will if you're knowledgable on the subject), I just want to make sure.

That would be fine Alan as the PSU has 100ma in reserve after powering the device and is correct voltage. Only thought is the polarity of the PSU correct for the device ? just check that and it should be fine ( The +- on the output jack often neg on the centre pin and devices are often protected from reverse polarity but not always


HTH

Roger

Thanks Roger, polarity is ok.

Not a silly question at all Alan.

The way I remember the difference betwen amps and volts is this

You can plug anything into a 13 amp socket from a small table lamp to a power drill.
But if you try to run a (British) shaver on the wrong (American) voltage, it won't work.

Or the school analogy with the hose pipe. The amps represent the amount of water there is, the volts is the water pressure, the resistance is how narrow the hose is and the watts are the power the resulting jet of water has to knock you flying. Oh, and the polarity would be the direction of flow!

Any use?

Iain

Roger's answer is correct, there is no problem to use a 200mA device with a 300mA PSU as long as the DC polarity is not inverted. The contrary (300 mA device with 200 mA PSU) might cause PSU overheating an insufficient power for the device.

Didier

Hi Alan,
The appliance draws the current it needs,in your case 200ma. Provided the voltage is correct and as mentioned,the polarity,it will only draw 200ma regardless of the capability of the power sourse,- our old friend Ohmns law, current equals voltage divided by resistance.
Des.