Will there be a display of numbers if the voltmeter is directly connected to both ends of the power

1. The voltage will be displayed;

2. The indication of voltage is the voltage of the power supply;

3. There is no necessary relationship between whether the voltmeter has an indication or whether it is open, and if the ammeter is open, there is no indication;

4. It is recommended that you look at the working principle of the voltmeter, the voltmeter is actually an ammeter (internal), and its indication is actually the indication of a period of current, but it is converted into the indicator of voltage, and the internal structure of the voltmeter is more complicated. If you are still a junior high school student, just remember that the voltmeter is connected to both sides of the power supply and will show the voltage of the power supply.

"Seeing infinity" is not really infinity.

First of all, we must know that in the voltmeter, there is a magnet and a wire coil, after passing the current, the coil will produce a magnetic field (it seems that this content is more than what you are currently learning, it is to be learned in the second semester of the second year of junior high school, but you must know the electromagnet), so that the coil will rotate under the action of the magnet after being energized, which is the head part of the ammeter and voltmeter.

The current that can pass through this meter is very small, and the voltage that can be borne by both ends is also very small (certainly much less than 1V, maybe only 0.00 volts or even smaller), in order to be able to measure the voltage in our actual circuit, we need to connect a relatively large resistance to this voltmeter in series to make a voltmeter. In this way, even if a relatively large voltage is added to both ends, most of the voltage is applied to the large resistance we add, and the voltage on the meter head will be very small.

It can be seen that the voltmeter is an instrument with a large internal resistance, which should generally be greater than a few thousand ohms.

It will be displayed, it is the power supply voltage. The voltmeter measures the power supply voltage at this time.

However, it is not possible to connect the ammeter directly on both sides of the power supply.

Yes. The supply voltage is displayed, but be careful not to exceed the range.

The voltmeter is connected to the two poles of the power supply, which is directly the voltage of the power supply.

In the event of a short circuit, the voltmeter has "almost" no indication.

It is said that it is almost because the voltmeter is essentially a combination of a resistor with a large resistance value in series in series, so in general, when it is determined that when it is short-circuited, the resistance of the short-circuit branch is infinitely small, and the voltmeter connected in parallel with it will of course almost no current pass. At this time, if it is a pointer-type voltmeter, because the range and minimum scale are too large, there is generally no indication. However, if it is a precision voltmeter with a precise digital display, it can measure a very small voltage (the size is equal to the minimum voltage at both ends of the short-circuit part) and so on

This should be seen from the principle of the voltmeter.

A voltmeter is a small range ammeter (G-meter), commonly known as a meter head, and then connected in parallel with a shunt small resistor.

According to what you said, then you can consider that an electromotive force (that is, voltage, I don't know if you are in high school) is connected to the power supply, then you have to consider the internal resistance of the voltmeter.

Generally, the resistance is different for different voltmeters. With the same voltage, i=u r. As I just said, the essence of a voltmeter is that a galvanometer is connected with a small resistor in parallel, and the current flowing through the voltmeter is different, and the indication is also different.

There is an error in the voltmeter, it's just a matter of how much. This phenomenon is inevitable in engineering technology, in fact, as long as the error does not exceed the allowable value, it will not have a serious impact on the project.

If it is confirmed that it is the same voltage, and that it is measured correctly and accurately read, then the problem may be with AOn the meter, you can first check whether the meter is working properly (replacement of internal batteries, etc.). b.

Confirm the stability of the voltage being measured. c.When the same voltage is measured on different meters, the results are approximately the same.

OK. If two DC power supplies with 5V power supply are connected in parallel, the measured voltage is 5V; If it is connected in series, the measured voltage is 10V. Be careful not to reverse the positive and negative terms when wiring.

The circuit connection method given is wrong. 220V power supply 220V switch 220V load, this is a complete stand-alone system and cannot be connected in series with the test system. The 5V test system should have a 220V 5V transformer, which supplies power to the 5V voltmeter and ammeter, and tests the shunt current on the 220V line; The 5V test system is relatively independent of the 220V operating system.