In daily life, if we touch the electrical wire with our bare hands, it will cause electric shock.
Electric shock will bring electric shock injuries to the human body, which will lead to damage to internal organs and even sudden death when serious, so we must pay attention to the safety of electricity, especially for people who do not understand electricity, do not try to repair household circuits personally. Speaking of electric shock, here is an interesting question, we all know that the transmission of current takes time, so if we have a very long wire, such as a very long wire with a length of 10 million kilometers, we hold one end of the wire, let people turn on the power supply at the other end, and then turn off the power before the current arrives, will the electric shock still occur? If you have a certain knowledge of electricity, then it should be clear that this question is actually very unprofessional, because only the length of a wire is given here, and there is no explanation for the material and cross-sectional area of the wire.
It's true that this is a less professional problem, but there is no need to be too entangled, because for a length of 10 million kilometers, the material of the wire is actually not so important, unless it is a superconducting material.
The so-called wire is a kind of conductor, its role is responsible for the transmission of current, and there are many conductor materials that can be used to make wires, but no matter what the material, it has a resistivity. When we turn on the current, the electricity does not go from one end to the other without loss, and a part of the electrical energy will be converted into thermal energy during the transmission process, and the specific amount of conversion is closely related to the resistivity of the conductor material. It should be noted that resistivity and resistance are not the same thing, resistivity is a physical quantity used to describe the resistance characteristics of a substance, and the resistance of a wire is related to its length and cross-sectional area in addition to its resistivity.
Other things being equal, the longer the length of the wire, the greater the resistance of the wire and the greater the wear and tear that occurs when the current is transmitted through the wire.
For example, copper is a conductor material with very little resistivity, and its resistivity is 0.01851Ω.mm/m. Resistivity is equal to the resistance of the object multiplied by the cross-sectional area of the wire and then divided by the length of the wire, from this formula can be seen, unless the cross-sectional area of this wire is ridiculously large, otherwise at a length of 10 million kilometers, even if it is a copper wire, the resistance of the entire wire will be amazingly large, so the power that finally reaches the end will be exhausted, whether the power is turned off or not, the person on the other end of the wire will not be electrocuted.
Since it is an interesting brain hole problem, let's not dwell on it so much, let's assume that this 10 million kilometers long wire is a superconductor.
The so-called superconductor is a conductor with a resistivity of 0, and the current transmitted in such a conductor will not cause any loss, so does the superconductor really exist? At present, many countries in the world are conducting research on superconductors, and it is generally believed that there are superconductors in theory, but unfortunately, no country has really found a superconductor with a resistivity of 0. Now let's go back to this interesting brain hole problem, now that the problem of current transmission loss is solved, we have to see how long it takes for the current to travel from one end to the other. Regarding the transmission of current, if you do not understand electricity, you may have some misunderstandings, mistakenly thinking that the current starts from the power supply through the entire wire to run to the other end, but in fact this is not the case.
In fact, electrons are ubiquitous, that is, electrons are originally present in various parts of the wire, but when the power is not connected, the movement speed of these electrons is very slow, only about 0.75 mm per second.
When the power supply is turned on, a closed circuit will be quickly formed, at this time an electric field will be formed at both ends of the conductor, so that each electron in the conductor begins to move, and the electrons in the back push the electrons in front, like a queue, constantly pushing the electrons in front to produce directional motion, so the current appears. Theoretically, the current travels in the wire at the same speed as the speed of light, that is, 299792458 meters per second. For a 10,000 km wire, the time required for current transmission is about 33.3 seconds.
Since it takes 33.3 seconds for current to be transmitted to the other end in such an ultra-long wire, we have plenty of time to turn off the power before the current arrives, so if we turn off the power supply 10 seconds after the power is turned on, will the person at the other end still be electrocuted? The answer is yes.
After the power is turned off, the conduction of the current does not stop, so whether the power is turned off 10 seconds after the power is turned on, the person on the other end will be electrocuted at the 33.3 seconds after the current is turned on. That is to say, as long as a closed circuit is formed between the wire, the human body and the earth, then no matter how long the power is on, even if it is only 0.1 seconds, the person on the other end will be electrocuted.