A passive linear two terminal network with a capacitor in parallel reduces the current

Experimental principle The cathode ray oscilloscope, referred to as an oscilloscope, is an extremely versatile electronic measuring instrument that converts electrical signals into images that can be directly observed on a fluorescent screen. There are many types of oscilloscopes, which can usually be divided into general-purpose, multi-trace and multi-line, memory storage, logic special, etc. The oscilloscope selected in this experiment belongs to the general dual-trace type, which is suitable for teaching use.

A single trace oscilloscope can only measure one electrical signal without an external device, while a dual trace oscilloscope can measure a single electrical signal or observe two electrical signals at the same time. During the experiment, when it is necessary to observe or compare the waveforms of two signals at the same time, it is more appropriate to choose a dual-trace oscilloscope. A block diagram of a dual-trace oscilloscope is shown in Fig.

It has two vertical signal input channels, Y1 and Y2, when the electronic switch composed of electronic wires is connected to the YL channel, it is controlled by the signal U1, and the waveform of the U1 signal is displayed on the phosphor screen; Similarly, when the Y2 channel is turned on, the waveform of the U2 signal is displayed on the phosphor screen. If the electronic switch alternates between channels Y1 and Y2 at a high enough speed, both the U1 and U2 signal waveforms can be observed on the phosphor screen due to the afterglow of the phosphor screen and the visual persistence effect of the human eye. Because the spurious interference of external electromagnetic waves is easy to enter the oscilloscope, the connecting line and grounding point must be selected correctly.

The oscilloscope housing is an input endpoint (the other end point is a cable), so in most experiments, the oscilloscope housing, the chassis of other equipment, and the reference potential points on the line should be connected together, called "common ground", that is, the common point potential is zero. If the grounding is unreliable, the waveform on the screen will float up and down, affecting the normal measurement work; If the wiring is incorrect, the instrument may also be burned. When using an oscilloscope, pay attention to whether the position of the knob is misaligned, because the fastening screws on the cap cover of the knob switch often slip.

When the knob switch is already in the limit position, do not turn it hard again to avoid damaging the switch. In this experiment, the sinusoidal voltage and the rectangular impulse voltage are measured, and their waveforms are shown in the figure. Figure 7-2(a) shows the sinusoidal voltage, and its amplitude um, peak-to-peak up-p, and rms values can all represent the magnitude of the sinusoidal quantity, but it is more convenient to measure up-p with an oscilloscope.

Since the frequency f=1 t, the frequency can be calculated by measuring the period t. Figure 7-2(b) shows the rectangular impulse voltage, which can be described by three parameters: period t, pulse width tp, and amplitude up. The ratio of tp to t is known as the duty cycle.

Experimental content.

For inductiveness, the current increases to capacitance after connecting a small capacitor in parallel, and vice versa, it is inductive, and I don't know anything else before I learn it.

3. The port voltage and current of a linear passive two-terminal network are u=22045v, 1=10105a, -|, respectivelyVoltage, hello dear According to the description of the topic, we can simplify this linear passive two-terminal network Jingdou Hall into an equivalent circuit. where the port voltage is u=22045v, the port current is i=10105a, and the network is a -||Voltage. Since the network is passive, it cannot provide any power.

As a result, the current is dissipated inside the circuit, resulting in zero power loss inside the circuit. According to Ohm's law and Kirchhoff's voltage law, we can list the following equation for the circuit: u = i * r + i * 2r + i * r where r is the equivalent resistance.

Therefore, we can get the equivalent electric pin tunneling equation under bright and hidden conditions: U = 4IR substituting U=22045V, I=10105A, we can get: R = U 4i) = Therefore, the equivalent circuit of the linear passive two-terminal network can be expressed as a resistor.

In the end, the answer is: the equivalent resistance of the linear passive two-terminal network is . Hope mine is helpful to you.

If you have any further questions or need further explanation, please feel free to let me know.

Summary. 3. The port voltage and current of a linear passive two-terminal network are u=22045v, 1=10105a, -|, respectivelyVoltage: U1 = 141 2 100, U2 = , U3 = .

i0=10，i1=，i3=3/√2=。φ1=-90°-（30°）=60°，φ3=90°-60°=30°。

3. The port voltage and current of a linear passive two-terminal network are u=22045v, 1=10105a, -|, respectivelyvoltage, 3 The port voltage and current of a linear passive two-terminal network are u=22045v, 1=10105a, -|, respectivelyVoltage: u1=141 2 100,u2=,line grip u3=clap with stupid 2,i1=,attack i3=3 2=. φ1=-90°-（30°）=60°，φ3=90°-60°=30°。

If the network is composed of pure inductive and capacitive elements, it is called a pure reactance two-terminal network. 2.If it contains resistive elements or takes into account the loss of inductance and electric key slag capacitance elements, the bent sail is called a lossy two-terminal network.

1) A small capacitor of appropriate capacity is connected in parallel at the passive network port (ingress) under test. When a small capacitor c is connected in parallel to the ports of a port network, if the small capacitor c zsinr,a, it is judged according to the increase or decrease of its total current. If the total current increases, it is capacitive; If the total current decreases, the shellfish is inductive.

In Figure 1(a), z is the impedance of the passive network to be tested, and c is the small capacitance connected in parallel. Figure 1(b) is the equivalent circuit of Figure 1(a), where g and b are the conductance and admittance of the impedance z of the passive network to be measured, and b is the admittance of the small capacitor c in parallel. Under the condition that the RMS value of the terminal voltage remains unchanged, the analysis is carried out according to the following two cases:

Let b b b", if b increases, b"also increases, then the current i in the circuit increases monotonically, so it can be judged that b is capacitive. Let b b b", if b increases, and b"If the current i decreases first and then increases, as shown in Figure 2, then B can be judged to be inductive. From the above analysis, it can be seen that when b is capacitive, there is no special requirement for the value c of the parallel small capacitance; And when b is sensual, b <|2b|It has the meaning of being judged to be emotional.

b>|2b|, the current increases monotonically, which is the same as when b is capacitive, but it does not mean that the circuit is inductive. Therefore, b<|2b|It is a reliable condition for judging the nature of the circuit.

I didn't write it, I pasted it.

Summary. Hello. If the equivalent impedance of a two-terminal network is a series combination of resistance and capacitance, this indicates that the network is (inductive).

If the equivalent impedance of a two-terminal network is a series combination of resistance and capacitance, this indicates that the network is ().

Hello. If the equivalent impedance of a two-terminal network is a series combination of resistance and capacitance, this indicates that the network is (inductive).

In an inductive circuit, the phase relationship of voltage and current is ().

I'll get back to you in a minute.

In an inductive circuit, the phase relationship between voltage and current is that the voltage is ahead of the current.

If you have any other questions, you can continue to consult me.

When the power component of the two-terminal network is less than zero, the network is capacitive or inductive.

The RLC series circuit consists of an inductor and a capacitor connected in series, and the resistor key module is the equivalent DC resistance of the inductor. When the applied signal frequency is equal to the natural frequency of the circuit, the total reactance is equal to zero, that is, the inductive reactance is equal to the capacitive reactance, and the circuit resonates; If the applied signal frequency is higher than the natural frequency of the circuit, the total reactance is greater than zero, that is, the capacitive reactance of the circuit is less than the inductive reactance, and the circuit is inductive; If the applied signal frequency is lower than the natural frequency of the circuit, the total reactance is less than zero, that is, the capacitive reactance of the circuit is greater than the inductive reactance, and the circuit is capacitive. Therefore, when the applied signal frequency is lower than the inherent frequency manuscript high rate of the circuit, when the total reactance of the code number is less than zero, that is, the capacitive reactance is greater than the inductive reactance, and the circuit is capacitive.

If you are asking, "If a passive two-terminal network has a terminal current and a terminal voltage, then the circuit should be capacitive." If so, you don't fully understand the passive two-terminal network, and you don't fully understand the nature of the circuit.

The so-called passive two-terminal network can be understood as a load with two wires leading out and not connected to the power supply. When this load is connected to the power supply, it will exhibit different properties;

When the terminal current is in phase with the terminal voltage, the circuit is resistive;

When the phase of the terminal current is ahead of the terminal voltage, the circuit is capacitive; It is equivalent to an ideal resistor in parallel with an ideal capacitor.

When the phase of the terminal current lags behind the terminal voltage, the circuit is inductive; It is equivalent to an ideal resistor in series with an ideal inductor.

The following questions you may not understand, but it is necessary to know.

The passive here refers not only to the absence of a pure power source such as a generator, but also to the absence of a "power source" such as a back electromotive force in the load, such as an electric motor. The motor is actually a power supply when it is running, but this back EMF can be converted into an inductance or even a capacitor in the calculation. You will not encounter such problems in your studies, but you may encounter similar problems in your actual work, but as long as you master the basic knowledge, these problems will be mastered with a little reasoning in practical work.

For example, some substations use motor idling to compensate for the power factor in the circuit.

The input impedance is obtained from the terminal voltage and current, and the real part of the impedance represents the resistance;

The impedance is imaginary, greater than 0 represents the inductance;

The impedance is imaginary, less than 0 represents the capacitance;

In a sinusoidal AC circuit, there are three phases of the phase relationship between the end current and the end voltage of the passive two-terminal network:

1. The terminal current is in phase with the terminal voltage, and the circuit at this time is resistive;

Second, the phase of the terminal current is ahead of the terminal voltage, and the circuit at this time is capacitive;

3. The phase of the terminal current lags behind the terminal voltage, and the circuit at this time presents inductance.