Incomprehensible Ohm s law. Who answered for me.

1. Ohm's law u=ir, at this time i=0, r is infinite, at this time it is not Ohm's law that is wrong, but a mathematical problem caused by the problem of our resistance value itself.

2. There is practically no infinite resistance. We can assume that r = 6 * 10 12 ohms (the general insulation resistance is less than this value), the internal resistance of the power supply = 1m ohms, then the current is about 10 (-12)a, the voltage drop on the internal resistance is equal to 1uv, and the voltage at both ends of the power supply is still 6v (1uv is not counted), which is in line with Ohm's law.

Here Ohm's law is called Ohm's law of closed circuits, and it should be said that closure can better reflect the relationship between the three physical quantities. So in this way, the voltage is not reflected.

Because voltage is the cause of the current generation, although there is no current, the voltage is still there.

For example, if you push a table with a force of 6n, the force here is equivalent to the voltage, and the movement of the table is equivalent to the current (because the current is generated by the directional movement of the charge), maybe you use 6n of force, but you don't push the table, but the force of 6n exists, and the table does not move, that is, there is voltage on it, and there is no current. Of course, this analogy is only used to understand the relationship between voltage and current, but in fact force is not the cause of the motion of the object.

In fact, it is not that there is absolutely no current passing through the insulator, but the current is so small that the instrument cannot measure it, so the current is considered to be 0. If we assume that the resistance of this insulator r = 100000000 ohms, then the current i = ampere, such a small current can of course be regarded as 0, but according to Ohm's law u = ir, the product of the two is exactly equal to 6 volts.

There is no absolute relationship between voltage and current, but there is a voltage to produce a current (current and voltage are subordinate).

When measuring the voltage at both ends of an electrical component with a voltmeter, it is connected in parallel on the electrical element. So the voltage measured in this question is actually the power supply voltage of 6V (the voltmeter is also connected in parallel with the power supply).

The resistance of an insulator is infinity.

u=iri=0

r = infinity.

0 * infinity is not necessarily = 0

n*(1/n)=1

n tends to infinity.

n*(1 n)=0*infinity=1

n*(1/2n)=1/2

6n*(1/n)=6

thanks

This is a closed circuit, and Ohm's law for closed circuits is to be used.

The voltage is fixed, and just because there is no current does not mean that there is no voltage.

Since R1 is the insulator, you measure the voltage when the battery is voltage.

Oh, this is not Ohm's law, it's a problem of resistance to this lack of law;

Law of resistance: r= l s; where is resistivity, which is determined by the material; l is the length of the wire; s is the cross-sectional area of the wire;

As you say, s are unchanged, so the resistance is proportional to the length of the wire;

l=(Pick old.)

Calculate the required length;

In superconductors, there is generally no constant voltage... It's u=0

The current in a superconductor is usually an induced current, which is the current that is generated by the electromagnetic induction of the magnet, and if r=0, then the magnitude of the current is irrelevant, and it will not be exothermic without resistance anyway.

As for the specific method of seeking ... My idea is, first of all, you have to know the total number of electrons in the system and the useful work done by the magnet during induction, and then because the resistance is zero, the energy is not dissipated, so all that work is converted into the kinetic energy of the electrons, and the average velocity of the electrons is obtained from the total kinetic energy of the electrons.

Then it is made up of the following formula:

Let n: denote the number of free charges per unit volume; Q: The amount of electricity of electrons; s: is the cross-sectional area of the conductor; v: The rate at which the free electrons move in a directional direction. )

i= q t =nqsv (1a=1c s) From this equation, the current can be obtained.

Once upon a time there were two teams of people, one called resistance and the other voltage! The voltage wants to cross the road, but the resistance refuses to ......The voltage is squeezed over, and which side has more people has the advantage! If there are more people with resistance, it will be more difficult for the voltage to pass by (the smaller the current, it can also be said that the smaller the amount), and if there are more people with the voltage, the easier it will be for the voltage to think about the past (the greater the current (**)))!

So ......There is great power in numbers!

Ohm's Law: You can analogy you can use a faucet.

Voltage is like water pressure, resistance is like the resistance of a water pipe, and current is like the speed of water.

The higher the water pressure, the greater the water velocity?

The greater the resistance of the water pipe, the smaller the water flow velocity?

So i=u r

The current is proportional to the voltage and the resistance is inversely proportional, that is, U=IR; Note that r has nothing to do with u,i. In fact, as long as you use it more, you can master it.

Ohm (1784 1854) was born into a modest family in Germany, entered university in 1805 and received a doctorate in philosophy in 1811. He worked as a tutor and secondary school teacher for more than 20 years, during which time he continued to work in physics, which led to the discovery of Ohm's law. He never married.

Inspired by Fourier's law of heat conduction, Ohm thought that the phenomenon of electric current was similar to the phenomenon of heat conduction, and conjectured that the current between two points in the wire might be proportional to some driving force between the two points, which he called "electrodynamics", or what is now called the potential difference. In order to test this conjecture, he conducted a long and extensive experimental study.

At first, he experimented with voltaic stacks as a power source, but failed to achieve the desired results because the electromotive force of the stack was not very stable. Later, at the suggestion of Boggendorff (1796 1877), he switched to thermocouples as a power source in 1826, thus ensuring the stability of the electromotive force. He skillfully used the method of balancing the torque of the torsion scale and the deflection torque of the magnetic needle acting on the electric current to measure the magnitude of the current.

As a result, he discovered a linear relationship between the strength of the "magnetic action" of the current (proportional to the strength of the current) and the "electrodynamic" force of the power supply, known as Ohm's law for the whole circuit. For a conductor, this law is shown to be proportional to the difference between the current and the electric potential, and its proportional constant is the resistance of the conductor, which is Ohm's law for resistive circuits.

Because the German academic circles at that time were under the influence of the "natural philosophy" of Schelling and Hegel, and did not care much about specific experimental work, Ohm's discovery did not immediately attract the attention of the domestic academic circles. His discovery was first rewarded by the Royal Society, which awarded him the Copley Medal, the highest honor in science at the time. It was only after Hegel's death that Ohm began to receive the treatment he deserved a long time ago.

Resistance resistance, the resistance of a substance to the electric current is called the resistance of the substance. The greater the resistance of a conductor, the greater the resistance of the conductor to the current. The resistance of different conductors is generally different, and resistance is a characteristic of the conductor itself.

A resistive element is an energy-dissipating element that hinders the current current. The magnitude of the resistance value of the resistive element is generally related to the temperature, and the physical quantity that measures the magnitude of the resistance affected by temperature is the temperature coefficient, which is defined as the percentage of the change in the resistance value for every 1 increase in temperature. Resistors are the most used components in all electronic circuits.

Ohm's law is the relationship between voltage, current, and resistance on a conductor, which can be expressed mathematically as: U=Ri, or R=U I, or I=U R. These three relationships are actually the same thing, but the emphasis of the expression is different.

For example, the first expression U=ri focuses on describing the relationship between voltage U (unknown) and current i (known) and resistance R (known), in the same way, the second focuses on describing the relationship between unknown resistance and known voltage and current, and the third focuses on describing the relationship between unknown current and known voltage and resistance. In other words, the first one is used to find the voltage, the second one is used to find the resistance, and the third one is used to find the current. Note:

The two variables to the right of the equal sign are both known quantities.

As for saying "when the resistance is constant, the voltage is proportional to the current", or "when the current is constant, the voltage is proportional to the resistance", and "when the voltage is constant, the resistance is inversely proportional to the current". Such descriptions are meant to express the relationship of mathematical formulas in words, but sometimes such descriptions are not comprehensive: they are only special cases when one of the physical quantities is constant, and the disadvantage is that they complicate simple problems, and it is easy for students to misunderstand when solving problems.

For example, when a sliding rheostat becomes larger, the question of whether the voltmeter becomes larger or smaller can be easily concluded by Ohm's law, but why are students not sure? The reason for this is that students are not sure which physical quantity is certain (i.e., has not changed). This requires students to understand that the current flowing through the sliding rheostat does not change as the center arm of the sliding rheostat moves (why not?). Therefore, according to the second explanation above, it can be concluded that "when the resistance of the rheostat increases, the voltage increases".

If students do not understand the premise of the above three descriptions, they may have the following misunderstanding: the resistance increases, causing the current to become smaller; When the current decreases, the voltage decreases, so you can draw the wrong conclusion that the voltage decreases. The reason for this error is that the student doesn't really understand "dang."

What exactly does the meaning of "certain" mean, and under what conditions will it not make a mistake when using it?

What needs to be pointed out here is: consult more teachers and really understand "dang." must be "exactly" to ensure that no mistakes are made in the application.

Space is limited, so I hope it will help you!

Ohm's law is a fundamental law that expresses the relationship between current, voltage (or potential), and resistance in a circuit.

1) Ohm's law for partial circuits.

The current (i) through the conductor is directly proportional to the voltage (u) across the conductor and inversely proportional to the resistance (r) of the conductor, i=u r

Transform the above equation to.

u=irr=u i(2) Ohm's law for all circuits.

The current in the closed circuit is directly proportional to the electromotive force of the power supply and inversely proportional to the sum of the load resistance and the internal resistance of the power supply in the circuit, i.e.

where i – the current flowing through the circuit in amperes (a);

e - power electromotive force, in volts (v);

r – load resistance in ohms ( ).

r – the internal resistance of the power supply, in ohms ( ).

If you want to consider the resistance of the connected wires, add the resistance value of the wires to the total resistance.

The reason why Ohm's law says that the current in a conductor is proportional to the voltage and inversely proportional to the current is for the same conductor, so the resistance is constant, so be careful when doing the problem.

As the resistance of the sliding rheostat increases, so does the voltage.

1) inversely proportional; (2) The current is inversely proportional to the length of the wire.