The adapter supplies the necessary voltage for the laptop to power on, charge the battery and run the various other parts that make up your notebook. It is very important to purchase and use the proper adapter. Buying and installing an incorrect adapter can cause damage to your laptop or simply not power it on. As for Dell laptops, for example, the Dell laptop battery charger has a label with a barcode on it. The Dell part number is imprinted on this sticker and it begins with 'CN' or 'D/PN' followed by a series of numbers. The first set of numbers is your part number. With this number you can now locate the correct charger or a compatible one.
Most new notebook power chargers are plastered and you cannot open and repair them. If the adapter is dead and it is highly recommended to purchase a new one. How can you tell if the AC charger is dead? Well, you can try testing it with a voltmeter. Let's say you are testing a 15V adapter and the output is 15.45V. That is normal and there is nada actually wrong if the output voltage reads a bit higher. But, if you are getting 0V, the adapter is by all odds DOA or 'dead.'
Now, if you accidentally have broken the adapter plug, you can try replacing it with a new one. Just make sure the new tip has the same size as the old one. Take out or cut off the old damaged plug and solder on a new one. It is wise to have some sort of technical skill before attempting to repair the battery charger. Always unplug the battery charger from the wall outlet before attempting a repair.
You can find the output voltage and amperage on a label behind the adapter. Also when you buy a new adapter, you can follow this simple rule: The output voltage must be identical, the amperage can be similar or higher than the original unit. For example, if your laptop requires a 19v-3.42A adapter, you can safely use a 19v-3.95A charger. Avoid the metal tip of the adapter from getting in contact with other metal objects because it can cause short-circuiting. Your laptop might get damage when a short-circuited charger is used. Don't place the notebook adapter in a cool place or near the air conditioner to avoid the device from getting moistened. Never pull the cord to detach the plug from the power outlet because the wire might be slashed or loosened.