Physics, about short circuits, physics of circuits under what circumstances will a circuit be short

At an ideal voltage source, your analysis is correct. However, in fact, both the power supply and the connected wires are internal resistance and resistance, which must be analyzed by Ohm's law of the whole circuit. After the wire short-circuits the electrical appliance, due to the extremely small resistance of the wire, after the voltage division is connected in series with the internal resistance of the power supply and the connection wire resistance, the voltage at both ends of the short-circuit wire is very small, that is, the voltage at both ends of the electrical appliance becomes smaller, and the specific amount is small, which should be almost zero.

It can be determined by the internal resistance of the power supply system and the resistance of the connected transmission line. Generally, the internal resistance of the power supply is relatively large compared to the wire resistance, and most of the voltage is divided into the internal resistance of the power supply, of course, the electrical appliances can not work normally, and at this time, it is not that there is no current through the electrical appliances, but it is negligible.

The resistance value is very small, which means that its electric ions (referring to the ions of the conductor) are very active, when there is a potential difference between the two ends of the resistance, there is almost no energy loss to make the electric ions flow, and the current appears, and the speed is very fast. And electrical appliances, relatively speaking, his resistance value is very large, for the potential difference, it will also appear ionic flow, however, his resistance value is very large, maybe his current has not yet been formed, and the wire connected in parallel with it has completed the large current, the large current will heat up through some conductors, when the conductor melting point is reached, it will be broken, such as the fuse is broken (tripped). The so-called short circuit, that means that the two ends of the power supply are directly connected by the wire, just like yours in parallel, which will cause the power supply to suddenly appear high current and be damaged.

Check out the explanation of the specific short circuit yourself.

The voltage at both ends of the parallel power is equal to the voltage at both ends of the branch, that is, theoretically the wire and the consumer are assigned the same voltage".

You're right, but this parallel circuit is connected in series with other circuit components, and you calculate the resistance of this parallel circuit? The parallel resistance is less than any one of the sub-resistors, and the resistance of this parallel circuit is less than the resistance of the wire. In series with other parts with large resistance (if it is domestic electricity, this circuit is connected in series with a high-voltage transmission line, and the resistance of this transmission line is very large, it can reach 100 ohms), how much voltage can be divided on it?

R is close to zero, the R line is a few hundred ohms, you will forget this, the voltage of the parallel circuit is almost zero.

The one on the 4th floor has very little resistance, so isn't the electrical power also very small? Why is it that the smaller the resistance, the greater the electrical power? "

p=uiThat's right.

i=u r, so p=u2r(2 for squared).

If the common power supply in the room, that is, the constant voltage source of constant output voltage, the resistance is small, the electrical power is large (pure resistance circuit, the electrical work is equal to Joule heating).

If it is a constant current source that outputs a constant current, then use p=i 2r, the smaller the resistance, the smaller the power, this kind of power supply is generally only available in the laboratory, this is the case you are talking about.

Isn't this the method of controlling variables?

Physics can't be a rigid formula, it must change.

It's not contradictory, and there's no need to get to the micro angle.

In the actual circuit, the power supply is to be considered!

In the circuit, the power is the sum of the two, if the resistance of the wire is very small, the power is very large, either tripping, or the wire is burned out! The first is common at home, the second is unlikely.

In the text, the main thing is to idealize the power supply (the power can be infinite), which is actually different! You've mixed up the reality with the ideal scenario.

If it is a battery, the battery has internal resistance, and after the current is large, the battery itself consumes a lot of electromotive force, and the external voltage is very small, which is not enough to drive the motor.

1. The electricity is passed through the wire (because the resistance of the wire is very small), that is, it will not be divided into equal voltages, so the electrical appliances do not work properly.

2 In the same way, electricity is passed through the wire, so there is no current in electrical appliances.

It's not a contradiction. /.The resistance of the wire is pitifully low.

This is very simple, when the power supply is overloaded, the voltage will drop, just like the motorcycle, when the voltage is 12V to start the motor to work, the voltage is only about 8V, and the performance is 9-10V

That's because the resistance is too small to be ignored.

1) A short circuit is a closed circuit when the power supply is directly connected by the wire without passing through the load. The short-circuit current refers to the current when the electrical appliance is not connected, which is equivalent to the current when the positive and negative phases of the battery are connected directly by finding a wire. (Usually this is a serious fault that should be avoided as much as possible, which can cause the circuit to burn out and fire due to excessive current.)

2) In a hybrid circuit, wires or switches are used to connect the two ends of a circuit component or load directly. (This is a local or partial short circuit that is required for a safety connection that does not cause burnout due to excessive current.) For example, in order to prolong its service life, when one of the filaments is broken and damaged, the special structure inside it will automatically connect the two ends of the small bulbs to make the other small bulbs work normally. )

A short circuit is when a circuit or part of a circuit is shorted. If the load and the power supply are connected by wires together, it is called a short circuit.

Causes of short circuits:

1. Short circuit is often caused by insulation damage or careless wiring. For example, equipment defects caused by aging equipment insulation materials and poor design, manufacturing, installation, and maintenance develop into short circuits.

2. Influence of meteorological conditions. For example, scintillation discharge caused by lightning strikes, overhead line disconnection due to wind damage, and power pole collapse caused by wire icing.

3. Man-made damage, such as the staff pulling the gate with load, and failing to exclude the grounding wire when overhauling the line or equipment.

Hazards: Sometimes tens of thousands or even hundreds of thousands of amperes will be generated. As a result, a large amount of heat is generated, which damages the equipment and the arc melts many components in a short period of time.

At the same time, the resulting current also brings a certain electromagnetic force, which can also damage the equipment. It can also cause major fire and injury incidents.

How to avoid short circuits:

1. Reasonable power supply layout and access mode, as well as reasonable grid structure, which is the preferred solution before adopting other current limiting measures, and is not suitable for existing power grids;

2. The development of higher voltage level power grids, the existing voltage level power grids are disconnected, layered, and partitioned, which has obvious current limiting effects and is also a fundamental current limiting measure, but sacrifices a certain degree of power supply reliability;

3. The effect of DC network current limiting is obvious, but the cost is high, and the economy is poor only from the perspective of current limiting, and it will take time for the practical application of multi-point DC transmission technology;

4. Conventional current limiting measures such as current-limiting reactors and high-impedance transformers are adopted, which have a certain current-limiting effect, but there are problems such as normal operation loss and may affect the stability of power grid operation.

1. What is a short circuit? Short circuit is a term used in electrical circuits. In a DC circuit, the power supply is divided into positive and negative electrodes.

If the positive and negative electrodes are not directly connected together by the electrical appliance, it is called a short circuit. In household circuits, if the live wire and neutral wire are put together, it will also constitute a short circuit. In industrial power circuits, any two circuits of different phases are directly put together, which will also constitute a short circuit.

For example, phase A thermal power and phase B thermal power are connected together. or the thermal power phase wire is connected together with the neutral line.

Second, the hazard of short circuit.

A short circuit is very damaging to the power supply. If we use a wire to connect the positive and negative electrodes of a dry battery, then in a short time, the battery will be depleted, and this time may only last a few seconds to ten seconds. Dry cell batteries will become floppy after a short circuit.

If the positive and negative wires of the dry battery are directly connected, due to the very high current, it may also cause an open flame and constitute a fire.

Third, why does it cause a short circuit? Short circuit formation is generally due to human carelessness. It is either caused by the aging of the circuit, or the circuit is overloaded for a long time.

Therefore, in life, we should pay special attention to preventing short circuits, use electrical appliances as you go, turn off the power when people go, and check the insulation layer of the line frequently. When installing the circuit, pay attention to distinguishing the live wire, neutral wire, or the positive and negative poles of the power supply, and install and lay the circuit in strict accordance with the electrical operation procedures to reduce potential safety hazards.

What is short circuit, open circuit, overload, leakage? Introductory electrician, don't be stupid and can't tell the difference.

Short circuit is divided into power short circuit and local short circuit, power short circuit is due to the wire is directly connected to both ends of the power supply without passing through the electrical appliance, which will lead to burning out the power supply and leading to disasters, while the local short circuit is to connect the wire in parallel at both ends of the electrical appliance, so that the current passes through the wire and does not pass through the electrical appliance.

Short circuit is a result of the loss of electricity that does not pass through the electrical appliances during operation, so that the current is too large!

A short circuit is when a circuit or part of a circuit is shorted. If the load and the power supply are connected together by wires, it is called a short circuit, the current provided by the power supply during the short circuit will be much larger than the current provided by the path, and the short circuit is generally not allowed, if the short circuit is serious, the power supply or equipment will be burned out. In the power system, the so-called "short circuit" refers to the connection between phases or between phases (or neutrals) outside the normal operation conditions of the power system.

The basic forms of short circuit in the three-phase system are: three-phase short circuit, two-phase short circuit, single-phase grounding short circuit, two-phase grounding short circuit. An abnormal connection (i.e., short circuit) occurs between phases or between phases (or neutrals), sometimes when a very large current flows.

Its current value is much greater than the rated current and depends on the electrical distance from the power supply at the short-circuit point. A short circuit is a low-resistance short circuit between conductive parts of different potentials, which is equivalent to a closed circuit directly connected by the wire without passing through the load. (Usually this is a serious fault that should be avoided as much as possible, which can cause the circuit to burn out and fire due to excessive current.)

A short circuit is a circuit in which the current does not flow through the electrical applicator and is directly connected to the positive and negative poles of the power supply. According to Ohm's law i=u r, we know that since the resistance of the wire is small, the current on the circuit will be very large when the power supply is short-circuited. Once you know such a large current, the battery or other power sources cannot withstand it, which will cause damage to the power supply; What's more, because the electricity and delay current are too large, the temperature of the wire will rise, and in severe cases, it may cause a fire.