If the circuit is open, isn t it broken, there is no current, why is there still voltage?

The current must be free electron movement in the current, the voltage is not necessarily, the same can be the same when the open circuit is open and the voltage at this time is the maximum after any load is connected, the open circuit is equivalent to the load resistance infinite.

The fuse is a metal wire that will melt after its temperature reaches a certain level, and the heat generated when the current is too large will cause the fuse to burn out q=i 2rt, q is the heat generated, r is the resistance of the fuse t t is the time.

1.The resistance of the voltmeter is very large, while the supply voltage of the circuit is very small, resulting in only a very small current passing through it, which is equivalent to an open circuit.

2.The fuse is made of an object with a low melting point and high resistance, and the current in the circuit reaches a certain level.

According to P=U2i, the heat of the fuse rises, and the temperature reaches the melting point of the fuse, and it blows to protect the circuit.

As long as there is a potential difference between the two poles of the battery, there is voltage, and how can there be a current when there is no load? The current is generated by the voltage flowing through the load Therefore, it is normal to have voltage when there is no current, and conversely, there will be no current if there is no voltage, and there is absolutely voltage if there is current!

The circuit can sometimes be understood by the water pipe at home, if the water on both sides of the water pipe is turned off, the water on both sides will not pass, but there can still be different pressures between the water on both sides, and if it is converted into electricity, there may still be voltage after the open circuit, which depends on whether the potential at both ends of the open circuit is the same;

Keep in mind the concepts and measurement methods of voltage and electrical current.

Voltage refers to the potential difference between two endpoints, voltmeter.

Parallel at both endpoints.

The current is the number of electrons flowing through a node per unit time, and the ammeter is cut into the node in series.

Therefore, when the circuit is open, there is no current and no voltage, this sentence is not entirely true, there must be no current, but there is still voltage.

There is a current and a voltage in the event of a short circuit, and this statement is not entirely true. There is certainly no voltage for the short-circuited part, but the voltage for the other parts may still be present, and there must be a current at the short-circuit.

This requires the specific measurement point to be specified: when the circuit is open, there is voltage but no current at the open circuit point, and when the circuit is short-circuited, there is current but no voltage at the short circuit point.

Wrong. General.

There is voltage but no current in an open circuit.

There is no voltage and no current for short circuit.

Wrong. When the circuit is open, there is no current and there is voltage.

The above explanation is typed out, "there is no current and no voltage when the circuit is open" is wrong. It has a power supply and a voltage, and disconnection is not a path, so there is no current. "There is a current and a voltage in the event of a short circuit" is true.

With the power supply, of course, there is a voltage, and it is a path, and the electrons can return to the positive electrode at the negative pole, and the current is naturally formed.

When the circuit is open, that is, when the circuit is broken, there is no current passing through, just like a wire is broken, the power is off, so it is not energized. But there is voltage, because the power supply does not stop working, so there will be voltage. In the case of a short circuit, there is only current, and if the line impedance is ignored, there is no voltage.

There is a voltage at both ends of the power supply, and some electrical appliances will induce voltage, so it is best to connect the case to a common ground wire.

The open-circuit voltage does not mean that the circuit does not supply power and there is voltage, but that the two lines with voltage are not connected to the load, and the voltage at this time is called the open-circuit voltage.

When the circuit is connected to the load, the internal resistance of the power supply and the line resistance must be divided, so the concept of open circuit voltage is introduced, which refers to the voltage that does not count the internal resistance and line loss of the power supply. In the event of a short circuit or heavy load on the service line, the load test voltage needs to be disconnected, which is the open circuit voltage tested.

It can be understood that the open circuit is equivalent to a resistor connected to both ends of the open circuit in the circuit, and the resistance value of the resistance is infinite, so that the current flowing through the resistance is infinitely small, then according to the law of voltage division of series circuits, the greater the resistance in a circuit, the greater the voltage (ur1=u*r1 (r1+r2+..)rn)), assuming that the resistance at the open circuit point is r1 and infinite, then ur1 is approximately equal to the power supply voltage u, so there is a voltage at the open circuit during the actual measurement, and the voltage value is basically equal to the power supply voltage value.

Voltages occur across the banks of a normal system open circuit point.

In the diagram, the circuit between points A and B is open (open), and the voltage between points A and B is 220 volts. If the breakpoint is closed (equivalent to the switch pressed), the voltage between the two points is zero (equivalent to the wire being directly connected, because the resistance of the wire is almost zero, so there is no voltage drop), and the current flows through the bulb (the circuit state is the path), and the light is on.

This is a normal phenomenon and can occur for two reasons:

First, there are conditions for generating static electricity, such as tiny particles and dust in the dry air;

The second is the existence of invisible resistance (before it was discovered), and the presence of conductive substances at both ends of the switch: insects, spider webs, water stains, stains and other conductive bodies.

In addition, there are some voltmeters (digital) with poor shielding or no shielding, which is easy to make the meter be interfered by stray electric fields.

There are many situations encountered in practical work that cannot be described in books and theories. When you carefully analyze, search, and eliminate, it is in line with books and theories.

It can also be understood like this:

An open circuit is when the circuit is not turned on, and although there is voltage at both ends of the power supply, it cannot form a current loop and the current is 0.

A short circuit is when the two poles of the power supply are directly connected by the wire, and because the resistance of the wire is approximately zero, although the current is very large, the voltage at both ends of the wire (or the two poles of the power supply) is U=IR (due to R=0)=0.

When the open circuit is opened, the voltmeter is equivalent to being connected to both ends of the power supply, and the power supply voltage is measured, because the internal resistance of the voltmeter is too large, so the current is close to zero. When the short circuit is shorted, the ammeter does not affect, and the voltmeter is short-circuited, so there is no indication. Can I do not? Cell phone called.