Laptop AC adapters are designed to be used with alternating current, the normal way of delivering electricity in this country. The part of the power supply cable that looks like a small box is the transformer, which converts the voltage from the mains supply to a lower power suitable for the components of laptops. AC adapters will become warm or even hot while in use so it is important that the adaptor is not put underneath other things that could trap the heat and potentially cause a hazard. Making sure that there is adequate ventilation helps to maintain the efficiency of the AC adaptor as well as protecting it from accidental overheating.
When laptops were first designed and marketed, it was thought that they would not be as popular as desktop computers because of the limitations in performance caused by having everything miniaturized. However, this has proved to be not the case, as laptops are very popular and many people have switched from desktop to laptop for both personal and business use.
Desktop computers rely totally on power from the mains supply so there is no need for any other power source. Of course, with laptops, the main feature is portability, so laptop chargers are an important part of the package. Most people using laptops don’t have the time to know much about how it works but have a rough idea how long their battery will last between charges, and this varies between makes and models, and depends on what the laptop is being used for. Using one of the larger models with many features will obviously drain the battery faster than one of the smaller laptops, but it is probably fair to say that you could expect anything between a couple of hours up to five or six hours, depending on these factors.
With a working day of about seven hours plus any leisure or home time you want to spend on your laptop, the importance of laptop adaptors becomes obvious. Batteries are no use once they are drained and the only solution is to plug in laptop adaptors and recharge. Laptops are designed to be used direct from mains power while the battery recharges, so the laptop power supply is no problem while you do this.