Is the resistance of superconductor zero? According to Ohm's law, I = u / R, r = u / I, if r = 0, isn't this Law meaningless?

Is the resistance of superconductor zero? According to Ohm's law, I = u / R, r = u / I, if r = 0, isn't this Law meaningless?

Of course, it makes sense, but this phenomenon only exists in theory. Because if the resistance is equal to 0, then the current will be infinite. This is what short circuit means in our life. But no matter what kind of wires, they all have internal resistance, only some are very small

On the calculation of superconductor current and other data
If the superconductor material is 0 resistance, then according to Ohm's law, u = IR, no matter how large the current is, the voltage is zero, or as long as the extremely weak voltage can produce infinite current, then the problem involved is big. I am very confused about this problem. To be concise, don't be too abstract

Ohm's law is just a macroscopic universal effect. It tells you that the current is inversely proportional to the voltage, which is defined as resistance. Experience listening to music has already told you that the current in superconductors is generated by electromagnetic induction, rather than by the traditional sense that the current is generated by the voltage at both ends. The current in superconductors does no work, So you can think that there is no voltage at either end

Why is there current in superconductors?
If there is no potential difference in superconductor, how can there be current?

Superconductors have zero resistance, so there is no voltage drop
In addition, it has no potential difference but can flow current, which can be explained as follows: because the power source itself has potential difference, and superconductor is just a path for free electrons to pass through unimpeded

What are the characteristics of current in superconductors?

The most important characteristic of superconductors is that the resistance is zero when the current passes through them. There are some types of metals (especially titanium, vanadium, chromium, iron and nickel). When they are placed at a very low temperature, the resistance is zero when the current passes through them. In ordinary conductors, most of the current passing through them becomes heat energy due to resistance, so it is "consumed", In a circuit composed of an electromagnet made of superconductor (a coil through which the current passes, an electromagnetic field is generated). In theory, only one current can be sent to the circuit, so that the electromagnetic field can continue. Of course, there is a loss, It is impossible to realize this kind of "permanent motion", and we have to consider the necessary energy input, so that the superconductor can maintain the required bottom temperature (i.e. - 269 ℃, 4 ℃ higher than absolute zero) to produce zero resistance phenomenon
However, since the beginning of 80s, new materials have been discovered. New materials can form superconductors under the condition of getting closer to normal temperature. Various kinds of superconductors are being studied for the purpose of simultaneous interpreting these materials. The difference between this material and traditional materials is that it does not need cooling system.
Superconductivity was discovered in 1911 by Dutch hekker kamerin Onnes (1853-1926). For decades, no one has been able to explain it, In 1957, physicists John BARDIN (one of the inventors of transistor), Leon Cooper and John Shriver announced the "BCS theory". Current is a kind of free electrons flowing around metal ions, i.e. atoms with extra positive charges. The reason for resistance is that ions hinder the flow of electrons, The reason for the hindrance is the thermal vibration of atoms and the uncertainty of their position in space
In superconductors, pairs of electrons combine to form the so-called "Cooper pairs". Each pair of electrons exists as a single particle. These particles flow together as if they were a liquid, regardless of the resistance of metal ions. In this way, in fact, any potential resistance factor is involved
What happens in ordinary conductors
The picture above visualizes the concept of electric conduction, which is like the motion of a sphere (electron). It flows on an inclined plane (the inclined plane is equivalent to a conductor). Obstacles represent the irregular network structure of metal ions, which do not allow electrons to flow freely. This is the reason for the formation of resistance, This energy is converted into heat
What happens to superconductivity
In superconductors, electrons are grouped into so-called "Cooper pairs" two by two, and they behave as single particles, which is the same reason that gas molecules can be aggregated into liquid. Superconducting electrons are shown as a whole in the form of liquid, although there are obstacles caused by the oscillation of metal ions and the irregularity of metal ion network, It can still flow freely without being affected