How to judge the short circuit If the potential on a wire is not equal, is there a short circuit? What is it? Under what circumstances, a short circuit will occur. I want the truth. Don't worry, I can't understand it

If the resistance of a wire is not included, the voltage at both ends of the wire should be 0 under normal circumstances. If it is not 0, that is, the potential at both ends is not equal, it must be a short circuit. Short circuit refers to the short circuit of the power supply

Xiaoqian's newly purchased house has just been renovated, and part of the lighting circuit in the house is shown in the figure. During the acceptance of the project, Xiaoqian closed the switch S (all other electrical appliances in the house are disconnected), and the incandescent lamp l went out after a period of time. She tested the two holes of the socket in the figure with the electric pen, and found that the electric pen was luminous. She disconnected the switch s and tested the two holes of the socket with the electric pen again She will observe () (assuming there is only one fault)
A. When two holes are tested, the electric pen lights up. B. when two holes are tested, the electric pen does not light up. C. only when the hole on the left side is tested, the electric pen lights up. D. only when the hole on the right side is tested, the electric pen lights up

(1) When the switch S is closed, the incandescent lamp L lights up for a period of time and then goes out, indicating that the bulb and the live wire and the zero wire cannot form a path. It may be that the live wire is open, or the zero wire is open

How to explain heat from the micro perspective?
The reason why the object near the heat feels hot is because of infrared. What about the object touching the heat? Is it molecular impact?

Micro heat is the irregular movement of the molecules that make up the object. Work and heat transfer are the only two ways to change the temperature of the object. If you touch it, it belongs to heat transfer. That is, molecular impact changes the intensity of the motion of the molecules that make up the low temperature object

Microscopic explanation of heat transfer
What is the essence of heat?
In the process of heat conduction and radiation, how does heat transfer in the micro level?

The essence of heat is the motion of molecules
When two objects with different temperatures come into contact, the molecules of the object with high temperature move fast and have high energy. After collision, the energy will be transferred to the object with slow motion, resulting in the acceleration of the molecular motion of the object with low temperature and the rise of temperature. Radiation is the intense infrared emitted by the object with high temperature, which can increase the energy of the molecular motion of the object with low temperature. The temperature rises, hee hee

Microscopic explanation of thermal expansion and cold contraction
Especially solids can't understand

An object is made up of molecules. There is a gap between the molecules. As the temperature increases, the speed of molecular thermal motion increases, resulting in the increase of the spacing between the molecules and the volume of the object. On the contrary, as the temperature decreases, the spacing between the molecules becomes smaller and the volume of the object becomes smaller. This is a microscopic phenomenon. You don't understand the thermal expansion and contraction of solid because you are too rigidly attached to the macroscopic phenomenon

How to judge the short circuit If the potential on a wire is not equal, is there a short circuit? What is it? Under what circumstances, a short circuit will occur. I want the truth. Don't worry, I can't understand it