The relationship between open circuits and short circuits and voltmeters and ammeters

Open circuits are relatively easy to understand, as soon as one place is disconnected, the circuit is opened.

There are two kinds of short circuits, overall short circuits and local short circuits, also known as power short circuits and electrical short circuits.

A power break (overall short circuit) is when a wire directly connects the positive and negative poles of the power supply. A short circuit (local short circuit) is a wire that directly connects the two ends of the electrical appliance. It is easier to judge the overall short circuit, as long as you observe whether there is such a wire in the circuit, and directly connect the two ends of the power supply to determine.

This kind of short circuit is far more harmful than a local short circuit and is not allowed to occur under any circumstances, and it is due to a design or connection error that is not intended by the designer. Electrical short-circuits (local short circuits) are the focus of the exam, which is caused by design or connection operation errors, and is also intentionally designed by the designer in order to seek special functions of the circuit, such as the two states of heat preservation and heating of the rice cooker, which is intentionally designed for local short circuits.

In the experimental questions or multiple-choice questions, it is easy to make the wrong connection operation, resulting in the judgment and analysis of the short circuit of the electrical appliance. To give you a mantra that I have summarized: there is voltage but no current in the open circuit, and there is no voltage and current in the short circuit. When the circuit is broken, the circuit is broken and the voltmeter is indirect.

, the voltmeter will show the supply voltage, and the series ammeter will be connected.

There is no indication of the number, so it is called "there is an electric Dan Ji test Ken Yao Stable surprised to inquire about the excess ink pressure, no current". If there is a short circuit, the zero resistance will cause a large current, and the zero resistance will get zero voltage, so there is a current and no voltage.

Landlord, I feel that you are not clear enough, especially the problem of parallel circuits, and I have not explained the use of electrical appliances. Here is my foolish opinion, hope!

In a series circuit, when the short circuit occurs, the voltage representation becomes larger, smaller, unchanged or no indicator, and the current representation becomes larger, smaller, unchanged or no indicator?

A short circuit in series means that the wire is connected directly to the two poles of the power supply (the ammeter and voltmeter are not included), so there is no resistance in the circuit, that is, when the current passes through the wire, there is no resistance to hinder and no voltage can be generated! So the voltmeter has a 0 indication (no indication). Again, because there is no resistance, there is no obstacle to the passage of current, so the current is larger than when there is an electrical appliance or resistance.

In parallel circuits, when the voltage is short-circuited, the number becomes larger, smaller, constant or unindicated, and the current represents the number becomes larger, smaller, constant or unindicated?

Long story short) there are no electrical appliances in the circuit, even if there are many wires connected in parallel in the parallel circuit, he is still non-resistive, pay attention to the "wires"! Therefore, the voltmeter does not indicate the number, and the current indicates that the number becomes larger.

The short-circuit current is infinite, and the voltage is zero. The open circuit current voltage is zero.

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 neutral wires) outside the normal operation 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.

The short-circuit current is equal to infinity, the voltage is zero, and the current of the power supply does not pass through the load, but flows directly from one end to the other to form a short circuit, which is quite harmful!

The open circuit current is equal to zero, the open circuit voltage is equal to the power supply voltage, the line is open, and the load cannot work normally.

The voltage is zero at infinity when the current is shorted, because the short-circuit is the absence of resistance.

The short-circuit current is zero, and the voltage is the supply voltage, because the open circuit means that the two ends are not connected, and the resistance is positive and infinite.

The short-circuit current is quite large and dangerous, for example, the short-circuit burns out the electrical appliances and the wire insulation are fused together and are easy to catch fire. The voltage is only the same as the original, except that the current is overpowered. The breaking current is zero, that is, the circuit has been disconnected, and there is no current and no voltage.

1. Open circuit: ammeter = 0;

Voltmeter. (1) Parallel connection with voltmeter.

The circuit is broken, and the voltmeter is approximately the mains voltage.

2) The circuit other than the parallel connection with the voltmeter is broken, the voltmeter Xunxian = 02, short circuit: the ammeter has an indicator.

Voltmeter: (1) The circuit connected in parallel with the voltmeter is short-circuited, and the voltmeter voltage is 02) The circuit connected in parallel with the voltmeter is short-circuited, and the voltmeter = power supply voltage.

in series circuits.

If it is an open circuit, the entire circuit will be disconnected and not energized; If it is a short circuit, the circuit is still closed and current can pass through.

in parallel circuits.

If it is a broken circuit, when it is a branch road, the branch road should be disconnected and will not affect other branches; On the Qingtan Trunk Road, the entire circuit will be disconnected and powered; If it is a short circuit, it is equivalent to a wire, which will affect the current of the entire parallel part of the circuit.

In a circuit, if the current does not flow through the consumer and is directly connected to the two poles of the power supply, the power supply is short-circuited.

When the circuit does not close the switch, or the wires are not connected properly, or the electrical appliances are burned out or not installed properly (such as putting a voltmeter.

in series) when the entire circuit is disconnected somewhere. A circuit in this state is called an open circuit (also known as an open circuit).

Voltmeter open circuit and short circuit are two different situations that have different meanings and effects in circuit measurement and operation.

Open circuit:

An open circuit is when a wire or component in a circuit is interrupted, resulting in no or very limited current flow. When measuring voltage, if there is an open circuit in the circuit to which the voltmeter is connected, the current cannot pass through the voltmeter, and the voltmeter will display a voltage value of zero, i.e., the open circuit voltage will be displayed. In the open state, the voltmeter acts as an open switch and cannot measure the voltage value.

Short circuit:

A short circuit is a direct low-impedance connection between wires or components in a circuit, resulting in an unrestricted passage of current. When measuring voltage, if there is a short circuit in the circuit connected to the voltmeter, then the current will pass directly through the short circuit part, and the voltage value displayed by the voltmeter will be very close to zero, that is, the short circuit voltage will be displayed. In the short-circuit state, the voltmeter is equivalent to a very low-impedance load and cannot measure the voltage value normally.

Difference: In the case of an open circuit, the voltmeter cannot measure the voltage value and shows that the open circuit voltage is zero.

In the case of a short circuit, the voltmeter shows a voltage value close to zero, but in fact a small part of the current passes through the voltmeter.

In the actual measurement, we should avoid the situation of open circuit or short circuit of the voltmeter, so as not to affect the accuracy and safety of the voltage measurement. If an open or short circuit is suspected, the fault should be checked and troubleshooting, the circuit should be properly checked and re-measured.

Voltmeter open circuit and short circuit are two different fault situations that have different characteristics and effects.

1.Open circuit: When the voltmeter is measuring the bridge and the circuit is disconnected, it is called an open circuit.

This means that there is no complete current formation between the measurement points back to the Sunlu path. An open circuit causes the current to not flow, so the voltmeter cannot properly measure the voltage in the circuit. Open circuits are usually caused by a switch not being turned on, a broken wire, or a faulty connection.

2.Short circuit: When the voltmeter is measuring the circuit, if a short circuit occurs between the measurement points, it is called a short circuit.

This means that a direct connection is formed between the measuring points with a low impedance, and current can flow from one measuring point directly to another via a short circuit. A short circuit can lead to an abnormal increase in current, which can lead to dangerous conditions such as overload, burned circuit components, and even electric shock. Short circuits are usually caused by short circuits in wires, damaged components, or faulty connections.

Therefore, there is a clear difference between open circuit and short circuit in voltmeter measurements. An open circuit can cause the voltage measurement to be zero or not displayed, while a short circuit can cause an abnormal increase in current, which can lead to damage to the measurement equipment or a safety hazard. Open and short circuits should be avoided in the measurement to ensure accurate and safe voltage measurements.

Breaking the circuit means that the road is impassable.

A short circuit means that there is a road that is very smooth without resistance.

The resistance of the voltmeter is large, and the current passing through it is small, which is equivalent to an open circuit.

1. Overview of voltmeter.

The traditional pointer voltmeter consists of a sensitive galvanometer with a permanent magnet inside the sensitive galvanometer, and a coil composed of wires is connected in series between the two binding posts of the galvanometer, and the coil is placed in the magnetic field of the permanent magnet and connected to the pointer of the meter by a transmission device. Most voltmeters are divided into two ranges. The voltmeter has three binding posts, one negative binding post, two positive binding posts, the positive pole of the voltmeter is connected with the positive pole of the circuit, and the negative pole is connected with the negative pole of the circuit.

2. Principle. Traditional pointer voltmeters and ammeters are based on one principle, which is the magnetic effect of electric current. The higher the current.

3. Voltmeter principle.

The greater the magnetic force generated, the greater the swing of the pointer on the voltmeter, there is a magnet and a wire coil in the voltmeter, after passing the current, the coil will produce a magnetic field, and the coil will be deflected under the action of the magnet after being energized, which is the head part of the ammeter and voltmeter.

Because the voltmeter should be connected in parallel with the measured resistance, if the sensitive galvanometer is directly used as the voltmeter, the current in the meter is too large, and the meter will be burned out, so that a large resistance needs to be connected in series in the internal circuit of the voltmeter, so that after the transformation, when the voltmeter is connected in parallel in the circuit, due to the effect of resistance, most of the voltage added to both ends of the meter is shared by the resistance in series, so the current through the meter is actually very small, so it can be used normally.

When a voltmeter is connected in series in a circuit, it will cause an open circuit.

Fault phenomenon of series circuit:

1. Open the road. Also ode to Bi Sui as "Broken Circuit").All electrical appliances do not work, and the ammeter has no indication, only the voltmeter that collapses on both sides of the breakpoint has an indication, and the indication is close to (or equal to) the power supply voltage.

2. Short circuit. Some of the electrical appliances that are shortened are not working, and the ammeter has an indicator, and the voltmeter connected to both ends of the short-circuited electrical appliance has no indicator, and the voltmeter connected to both ends of other electrical appliances has an indicator.

Judgment of open circuit and short circuit.

1. Judgment of open circuit.

1. If the electrical appliances in the circuit do not work (often the light is not on), and there is no current in the circuit, the circuit is open.

2. If the voltmeter is connected in parallel with each place, then there is an indication and it is relatively large (often expressed as equal to the power supply voltage), and the circuit between the two binding posts of the voltmeter is open (except for the power supply).

Second, the judgment of short circuit.

1. If some of the electrical appliances in the series circuit or series part cannot work normally, and the other parts of the electrical appliances can work normally, the part that cannot work normally will be short-circuited.

2. The voltmeter is connected in parallel with each part, and the voltage of the wire part is zero to indicate that the wire is normal, if the voltage at both ends of a certain electrical appliance is zero, the electrical appliance is short-circuited.

Whether it is connected in series or in parallel, if it is a short circuit, the ammeter.

The indication increases because the electrical resistance is very small after the short circuit, so the resistance is very large, and the voltmeter.

It is non-indicative, because the resistance is small after a short circuit and the resistance of the voltmeter is large, so the current does not flow through the voltmeter, resulting in the voltmeter without an indicator.

When there is an open circuit, the current representation is zero, because the circuit is broken and no current flows through the circuit, so the ammeter has no indication. However, at this time, don't think that the voltmeter does not have an indicator, if the electrical appliance is disconnected, then the voltmeter indicator should increase (it may not increase, the indicator does not change) It depends on the situation, if the voltmeter Yu Xiang pin only measures the voltage of an electrical appliance and is a series circuit.

, its indication will increase, because after the circuit is opened, the voltage is directly measured by the power supply voltage; If the total voltage is measured by a series circuit voltmeter, then its indication does not change. And parallel circuits.

Whether it is connected in series or parallel, if there is a short circuit, then the voltmeter added to both ends of the load will immediately return to the side letter 0, and the ammeter will burn out (if there is a protective starting bucket resistor, the current indication number will increase);

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 burn out the power supply, lead to disasters, and object erection, and 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.

In the above diagram, if the voltmeter, L1, and L2 are removed, and the switch K is closed, the power supply of the circuit is short-circuited, and the power supply will be burned out, and the voltmeter is equivalent to a disconnected switch, so only the voltmeter is connected to the circuit, and there will be no short circuit in the power supply, and if the voltmeter is replaced with a wire, L2 will be short-circuited, L1 can emit light, and the current will pass through the wire below L2.