# What exactly are amperes anyway?March 14, 2011 1:53 PM   Subscribe

If I use a 19.5 volt 4.7 ampere adaptor with a device that calls for a 19.5 volt 3 ampere adaptor, will it cause any problems?
posted by matkline to Technology (8 answers total)

Amps are a measure of electric current. My understanding is that you get into problems when the adapter cannot put through enough current for the device; an adaptor that can put through more current than you need is not a problem, because the device will simply not draw that much current.
posted by Dasein at 1:56 PM on March 14, 2011

4.7A is the maximum output. Your device will only draw 3A. All other possible problems (check the polarity, etc) aside, this is fine in theory.
posted by kcm at 2:03 PM on March 14, 2011

your laptop will be fine but (as on preview already suggested) ensure polarity is correct (usually depicted with 2 concentric circles with a '+' attached to one of them.... likely the middle one)
posted by chasles at 2:06 PM on March 14, 2011

Not a problem. 4.7A is the limit of what it can put out, which means it is capable of supplying the required 3A. It's like having a car that can do 200mph - it won't have a problem driving 60mph on the highway.

As others have said, the polarity (arrangement of the positive and negative terminals) must match what is required as that would be a big problem if it were reversed.
posted by Diplodocus at 2:19 PM on March 14, 2011

To clarify, both adaptors are for Sony laptops
posted by matkline at 2:39 PM on March 14, 2011

Generally speaking, the voltage has to be the same and the current rating of the supply has to equal or exceed the current rating of the load.
posted by Chocolate Pickle at 3:33 PM on March 14, 2011 [1 favorite]

horsepower is probably a better analogy than mph, but yeah you'll be fine.
posted by russm at 3:34 PM on March 14, 2011

russm: "horsepower is probably a better analogy than mph, but yeah you'll be fine"

Horsepower is a terrible analogy notwithstanding the confusion with electrical power. Think of it as a pipe supplying a tap - if you need a certain flowrate, as long as the pipe is wide enough (the supply is rated to at least the necessary current), it can provide the required flowrate.
posted by turkeyphant at 6:27 AM on March 15, 2011

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