Updated on December 30, 2010

What exactly is a 9v DC adapter and what do I need to know before I get one? These two questions are the main points of focus in this article.

Plainly said, a 9v DC adapter transforms alternating current to 9 volts direct current. But wait, what exactly is direct current and alternating current? To try and be as simple as possible, alternating current, or AC, is the current that is available at home. It is the current or electricity which can be had from your wall socket. Direct current, or DC, on the other hand, is the type of electricity found in batteries.

In direct current, the flow of electric charge is in one direction. As previously mentioned, it is produced by sources such as batteries, solar cells, and electric motors. DC is commonly associated with low-voltage device such as gadgets and appliances that use batteries—laptops, portable music players, etc. All of these devices have voltage ratings and such can be rated anywhere from 3.6 volts up to 36 volts, or specifically lower than AC voltage.

In alternating current, the flow of electric charge periodically reverses direction. AC is the form in which electricity is delivered to residences and businesses. Any appliance that is plugged into a wall socket is an AC device. Worldwide, AC is usually delivered as 110 volts and 220 volts.

A correct DC adapter can be tricky. When you say “9v DC adapter,” there is no standard or one product that can be bought. The only thing that is constant is that it converts AC electricity to 9v DC. So looking back at that, there are things to consider such as AC voltage, polarity, size and types of input and output plugs to name a few.

Anyway, as a guide, below are some of the options you need to check and make sure of if you are in the market for a replacement adapter.

Input voltage

Input voltage is the voltage of your wall socket or where you will plug your adapter into. Obviously, this is standard per country so for example, in the United States, you are looking at a 110 volts input voltage.

Wall socket plug

Wall plugs are different all over the world and adapters can be bought to convert one form to another. If you are to buy your adapter locally, there shouldn’t be any problems regarding the compatibility of the plugs.

Maximum current rating of device

To avoid destroying your gadget, make sure it has a higher maximum current rating than what the adapter can offer. If not, you can destroy your device by giving it more “juice” than it can handle.

Input plug on device

Unfortunately, unlike wall socket plugs, there is no per-country standard on these things. In fact, manufacturers make it a habit to create unique plugs on their devices so that consumers will buy only original replacement adapters. If you do not have the right plug, your adapter is useless. However, if you have the right size and style, you still would need to look at polarity.

Output voltage

Final reminder

In any case, always make sure to check if original replacements are currently available. If not, make sure you know your devices exact model number—for example the serial and model number of your laptop—and buy only an adapter that is specifically made to work with your device.

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