What are Voltage, Current, Frequency, Power, DC and AC?

Current: We know that water can flow in a tube, and we call it water flow. In the same way, electrons can flow in the wire, and this flow of electrons is called an electric current.

Electric currents are generally symbolized"i"Denote. There is a difference between high and low water in the flow, and there is also a difference in the strength and weakness of electricity in the flow. The laughter of the electric current is expressed in terms of the intensity of the electric current.

The intensity of the current is numerically equal to the amount of electricity that passes through the cross-section of the wire in one second. The magnitude of the current is usually the magnitude of the current intensity. The unit that generally expresses the intensity of the current is amperes, referred to as amperes, with symbols"a"Denote.

In some circuits, the current flowing through is very small and is usually measured in milliamps and microamps.

The conversion relationship between them is:

1 amp = 1000 milliamperes (mA).

1 mA = 1000 microamps (A).

Voltage: As we all know, the reason why water can flow in the pipe is because of the difference between high and low water levels, and the water can flow from high to low. The tap water used in the city can flow out of the pipe as soon as the water gate is opened, because the water storage tower is higher than the ground, or because the pressure difference caused by the water pump.

The same is true of electricity, which is able to flow in the wire, also because there is a difference between high and low potential. This difference is called the potential difference, also known as the voltage. In other words.

In a circuit, the potential difference between any two points is called the voltage at those two points. Voltage with a symbol"u"Denote. The level of voltage is generally expressed in unit volts, referred to as volts, and is symbolized"v"Denote.

High voltages can be expressed in kilovolts (kv) and low voltages can be expressed in millivolts (mv).

The conversion relationship between them is:

1 kilovolt (kv) = 1000 volts (v).

1 volt (V) = 1000 millivolts (mV).

Broadly speaking, frequency is the number of times a thing appears in a unit of time;

In a narrow sense, frequency is the number of times a substance vibrates per unit of time.

For example, the frequency of a signal in physics is measured in time (seconds), and an event is a characteristic value of the physical quantity described (e.g., the peak of voltage, the pulse front, etc.). In mathematical probability, a unit quantity is a numerical interval, and an event is the occurrence of a described phenomenon.

Direct current refers to the current in a certain direction and the same size, and the flashlights we use and the batteries on tractors and cars are all direct current.

Alternating current refers to the current that is constantly changing in direction and size, and the electricity used in our common lamps and motors is alternating current. In practice, direct current is used with symbols"="Indicates that the AC is used with a symbol"~"Denote.

The difference between high and low potential is called voltage! The flow of electrons in a conductor driven by an electric tooth is called an electric current! Voltage is measured in volts!

It is represented by v! The unit of dot stream is amperes! I denote it with A!

The period of oscillation per second of an object or radio wave is called frequency! The unit of frequency is Hezhi! I display it with h!

The amount of work done per unit of time is called power! Electrical power is the product of voltage and current! The unit of power is watts!

I display it with W! Direct current is an electric current that does not change in direction and magnitude with time! Alternating current is an electric current whose direction changes periodically over time!

China's basic alternating current is a three-phase four-wire system! Voltage: 380 volts! Frequency 50 Hz per second!

Dude, this question is too basic, if you're going to do electricity!

It is still recommended that you take a look at the basic books of electricity in the morning, which can also be found on the Internet, and even junior high school textbooks.

The difference between DC voltage and AC voltage: DC voltage is the voltage whose direction and magnitude remain constant; AC voltage is the voltage that changes periodically in direction and magnitude.

Alternating current refers to an electric current that changes periodically in both magnitude and direction because the average operating value of the periodic current in a cycle is zero, which is called alternating current or alternating current for short.

The voltage value changes with time, but the voltage that does not change in direction with time is called a pulsating DC voltage. For example, the voltage at both ends of the flashlight battery and both ends of the bulb is DC voltage.

For direct flow, the voltage value can be processed directly, but for the AC volume, it is important to pay attention to the specific amount measured, whether it is an average or a valid value. Normal alternating current, because the positive and negative directions are symmetrical, has an average value of 0. Therefore, the measurement of alternating current is usually measured in terms of the effective value, and the so-called "effective value" can be understood as the equivalent measurement value of direct current, and in the case of alternating current of a sine wave, its effective value is equal to the root mean square value over a period of time.

DC is a constant voltage value, such as 12V, 24V is positive relative to 0V and will not change. In the case of communication, there is positive +12, +24 has -12v, and -24v relative to 0v, which changes with a certain period. He is a relative concept.

There is no relationship between frequency and voltage, and frequency has a great influence on capacitive and inductive loads.

The frequency is the indication that it is alternating current.

The relationship between current and voltage is Ohm's law.

In practice, there will be different associations depending on the situation.

Example 1: The voltage source is connected to a resistive load.

The voltage does not change, and the frequency has no effect on the current.

Example 2: The voltage source is connected to an inductive load.

The voltage does not change, and the higher the frequency, the lower the current.

Example 3: The voltage source is connected to a capacitive load.

The voltage is constant, and the higher the frequency, the greater the current.

The relation is.

Voltage = u*sin( t+ ).

Note that the voltage of the alternating current refers to the RMS!

The voltage of the alternating current that we usually say refers to its effective value, and the gelatinous value depends on the amplitude and frequency of the alternating current. When the amplitude of the two alternating currents is equal, the effective value with a high frequency is high. But the difference is not very large.

In an AC circuit, u=(r+j x)i. where =2 f, where f is the frequency.

Frequency is a physical quantity of periodic change, the unit is Hz, which is only related to the period change time, and has nothing to do with others.

v denotes the potential.

u indicates the RMS value of DC voltage or AC voltage.

So exactly it should be.

u r is right.

There is no special statement in this formula that u defaults to the voltage at both ends of r, and i defaults to the current in r.

If you don't change r, you will definitely go down i.

This is also the case in AC circuits, because this is a purely resistive circuit. (With the level of understanding that people have now, we can say this, and I don't know if they can say this in the future.)

Formula: u=(r+j x)*i

The x equal to zero in it means that the resistive circuit is independent of frequency, which is simplified: u=r*i

Frequency is dependent as long as there are active components in the circuit and they are not resistive (i.e., x=xl-xc≠0).

Explanation: X denotes reactance.

XL stands for inductive reactance.

xc stands for capacitive reactance.

z=r+jx represents impedance;

A pure resistive circuit means that there are only resistive devices in the circuit, and there are no energy storage components, capacitors and inductors;

A resistive circuit is one in which there is an energy storage element in the circuit, but x is equal to zero.

The inductive and capacitive reactions cancel each other out;

Active components and energy storage components refer to components such as inductors and capacitors that can store energy.

In impure resistive circuits, the impedance z=u i

Z sense = 2 fl

Z capacity = 1 2 fc

In this way, there is a relationship between the three. Can?

Many people are not clear about this question, and they often see plausible.

The correct answer is as follows -

DC voltage is a voltage that remains constant in direction and magnitude; AC voltage is the voltage that changes periodically in direction and magnitude.

There are two things to note here:

1. Direct current is based on voltage rather than current, and the current will change with the change of the load situation, as long as the voltage remains constant, it is direct current, such as the dry battery or stabilized power supply that supplies power to the radio, although its output current will change with the volume, but the voltage is constant, so it still belongs to the DC voltage;

Second, the change of AC voltage is a periodic change rather than a random change.

Summary. What are AC, DC, and current?

Hello dear, electric current refers to the speed of directional movement of electric charge, which is called current intensity, referred to as current.

Direct current refers to the current that does not change in the direction of the current.

Alternating current refers to an electric current that is constantly changing in the direction of the current.

There are a lot of differences.

Generally, batteries, storage batteries and other power sources provide direct current.

The electricity used at home is generally 220V alternating current, such as a TV or something.

The magnitude and direction of direct current generally do not change, while the magnitude and direction of alternating current do.

Today's power supply department provides three-phase alternating current.

What are AC, DC, and current?

What are AC, DC, and current? Hello dear, the current refers to the speed of the directional movement of the charge, which is called the current intensity, and the simple crack judgment is called the backup current. Direct current refers to the current that does not change in the direction of the current.

Alternating current refers to an electric current that is constantly changing in the direction of the current. There are many differences, the batteries generally used, the batteries and other power supplies provided are direct current, and the electricity used at home is generally 220V alternating current, such as TV or something. The magnitude and direction of direct current generally do not change, while the magnitude and direction of alternating current do.

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Direct current (abbreviated as DC): refers to an electric current that does not change in magnitude or direction with time.

Many electrical appliances, such as radios, speakers, and many other appliances that do not contain inductive components, are driven by direct current.

Alternating current (abbreviated as AC): The direction and magnitude of the current change over time. The generator of the power plant uses power to make the coil in the generator run, and the direction of the output current of the generator will change once every 180°, so the magnitude of the current will also change regularly with time, this kind of power supply is called"AC power"。

In daily life, how to distinguish between direct current and alternating current:

1. DC is DC, the current and voltage direction is consistent, and there is a "+" pole.

However, the voltage and current of direct current also fluctuate, for example, after the diode is rectified, before the unfiltered voltage is regulated, this is called pulsating direct current, but the direction of direct current is always the same. From positive to negative. It is common to have various types of batteries, such as mobile phones, flashlights, battery cars, computers, various toys and small household appliances.

Pay attention to the difference between positive and negative electrodes when using direct current.

2. Alternating current, abbreviated as AC.

Generally refers to a voltage or current whose magnitude and direction change periodically over time.

The advantages of alternating current are mainly manifested in the power generation and distribution: the use of alternators based on the principle of electromagnetic induction can be very economical and convenient to convert mechanical energy (water flow energy, wind energy?). Chemical energy (oil, gas?)

and other forms of energy are converted into electrical energy; Compared with DC power supplies and DC converter stations of the same power, the cost of AC power supply and AC substation is much lower; Alternating current can be easily boosted and stepped down through the transformer, which brings great convenience to the distribution of electrical energy This is the unique advantage of alternating current compared with direct current Its most basic form is sinusoidal current.