When you turn on an electric stove top burner with nothing in it (no pan), it will still heat up. Electric stove top burners work by passing an electric current through a heating element, which generates heat. This heat is transferred to the cookware (such as a pan) placed on the burner, which, in turn, cooks the food.
When there is no pan or cookware on the burner, the heating element is still active, and it will heat up. However, without a pan to transfer the heat to, the burner will continue to get hotter until it reaches its maximum temperature. Most electric stoves have temperature limiters or thermostats that regulate the heat to prevent the burner from overheating, but if the stove is old or faulty, it may continue to heat up until it's manually turned off.
It is important not to leave an electric stove burner on without any cookware on it, as it can waste energy and may pose safety risks, such as accidentally touching the hot burner or forgetting to turn it off, leading to potential burns or fires. Always ensure that there is a pan or cookware on the burner when it's in use to safely and efficiently cook your food.