According to Baidu Library, the voltage of dormitory is also 220 volts supplied by ordinary cities. If an independent electricity meter is installed in the dormitory of a university to measure the electricity consumption, generally, electrical appliances below 2000 watts can be used, such as hair dryers and small rice cookers. Generally, the power used in the dormitory is limited to less than one kilowatt, and an air switch is installed to limit the current. With unified power supply, high-power electrical appliances, such as hair dryers, can't be used in dormitories, because the air switch at the entrance of many dormitories is only 3 amps or 4 amps, which can use hundreds of watts at most, while hair dryers need at least 1000 watts and will trip automatically. Some dormitories are 500W, which means that electrical appliances with power higher than 500W cannot be used. In fact, it can't be used normally above 450W W, and the power of electric kettle is generally close to 1000W, so it is not suitable for use. You can buy low-power heaters, electric cups, rice cookers and the like, and the general power is between 200 and 300 W.