Dòng điện là gì? Đặc điểm tính chất của dòng điện

Electric current has been around for a very long time, it helps a lot to people in labor and production. So you understand all about electricity, What is electric current?? What are the characteristics and properties of electric current in different environments? formulas for calculating amperage, etc. The following article we will remind and summarize the knowledge about electric current for you!

What is electric current?

Electric current is the directional displacement of charge carriers. In an electrical circuit, current is generated when there is a movement of electrons in a conductor.

In electronics, current is the flow of electrons in a metal conductor, in a resistor, or the flow of ions in a battery or the flow of electron holes in a semiconductor material.

What is power source?

Power sources are electrical devices that are capable of supplying current for a long period of time for electrical equipment to operate. Each power source will have 2 poles, positive (+) and negative (-).

For example: Battery, Generator, Battery, Power outlet, …

What is amperage?

Concept:

• Amperage is a quantity characterized by the strength and weakness of an electric current.
• Amperage is the conventional unit of quantity of charge passing through a conductor per unit time.
• Symbol Amperage is I, unit is A (ampere)

Formula for calculating amperage:

The formula for calculating average amperage:

In there:

• I_tb is the average amperage (A).
• ΔQ is the amount of charge flowing through the measuring surface in the time interval Δt, the unit is C (coulomb).
• Δt is the measurement time, the unit is s (seconds).

Ohm’s law of current

Talking about electric current is talking about Ohm’s law. Ohm’s law is the change of electric current through the potential difference between the two ends of a conductor and the resistance the object has. We have the formula:

I = U / CHEAP

In there:

• I is the current through the conductor, the unit is A (or Ampere).
• U is the potential difference between the two conductors, the unit is V (or Volt).
• R is the resistance representing the ability to resist the flow of current in the conductor, the unit is Ω (or Ohm).

Current direction convention

The current in the conductor can move in any direction, when there is a current I in the circuit, the conventional current direction should be marked, usually by an arrow on the circuit diagram. That is called the reference direction of the current I, if the current moves against the reference direction, then I has a negative value.

There are two types of current, alternating current and direct current.

What is direct current (DC)?

Direct current, also known as direct current, is often abbreviated as 1C, or in English it has an abbreviated form of DC. Means “Direct Current“.

Direct current is a current that moves charges in a certain direction and does not change throughout the process.

The magnitude of the direct current is always constant and the frequency of the current is zero. Direct current is used in mobile phones, electric vehicles, electronic equipment, etc.

In addition, we also have the concept of DC voltage. Is the potential difference between two poles of direct current, the value is usually 5VDC, 12VDC, 24VDC.

The sources of DC current include the mains, electrochemical cells and photovoltaic cells. Batteries and other sources of DC current produce a constant voltage. This is called pure direct current and is represented by a straight, horizontal line on a voltage-time graph.

What is alternating current (AC)?

Alternating current is an electric current that changes its direction in cycles

The symbol for alternating current is AC in English (that is, Alternating Current).

The change of current during transmission is periodic in the form of a sinusoid. The magnitude changes with time, free electrons move in 2 directions. Alternating current converts from high value to low value thanks to the transformer. Therefore, it is mainly used for transmission and distribution.

While DC current flows in one direction through the conductor, AC electricity flows in the direction of reciprocating motion. The direction changes between 50 and 60 times per second, depending on the electricity system of each country.

Alternating current is usually generated from alternators or converted from a DC power source.

AC is special in that the voltage can be easily changed, making it more suitable for long-distance transmission than DC.

What are the characteristics of electric current?

In different environments, charge carriers will have different corresponding conformations that create different nature of the electric current in the media.

currents in metals

The nature of electric current in metals is a directional flow of electrons in the opposite direction of the electric field.

Superconductivity: Is the phenomenon that the resistivity of a conductor suddenly drops to zero when the temperature of the conductor drops below a certain value Tc. This value of Tc depends on the conductor itself

=> Thus: Electric current in metal is the directional displacement of free electrons under the action of electric field.

Current in the electrolyte

In solution, salts, acids, and bases dissociate into ions.

An electric current in an electrolyte is a directional displacement of ions in an electric field in opposite directions.

The phenomenon of anode dissolving: is when the acid radical in the electrolyte solution reacts with the anode to create a solution-soluble electrolyte, the anode is worn away.

=> Thus: The electric current in the electrolyte is the flow of positive (+) and negative (-) ions moving in opposite directions. To the electrode, only the e goes forward, the amount of matter is deposited at the electrode, causing electrolysis.

Electric current in a gas

Under normal conditions, gases do not conduct electricity. It conducts electricity only when there is ionization of molecules in it.

Electric current in a gas is the directional flow of positive (+), negative (-) ions and electrons produced by an ionized gas.

When using a power source with a large voltage, a charge carrier nucleus appears in the gas.

Self-propelled discharge process is the maintenance of the discharge process when there is no longer an ionizing agent of the gas from the outside

Electric arc is a self-powered discharge process that creates an electric current through a gas and maintains a high temperature of the cathode so that it can emit electrons by the phenomenon of electron thermoelectric emission.

=> Thus: Electric current in a gas is a directional flow of positive ions (+) in the direction of the electric field and negative ions (-), electrons in the opposite direction of the electric field. These charged particles are produced by ionized gas. This is called a non-self-supporting conduction (discharge) process.

Current in a vacuum

The vacuum diode allows current to flow in only one direction, which is called rectification.

The flow of electrons accelerates and changes direction thanks to electric and magnetic fields. It is used in cathode ray lamps (CRTs).

=> Thus: Current in a vacuum is the flow of electrons from the negative (-) pole to the positive (+) pole under the action of an electric field. The nature of electric current in a vacuum is that Vacuum is a medium without matter and energy.

Current in a semiconductor

Some substances in the main group, group 4, such as Si and Ge, can conduct electricity or not conduct electricity under different conditions, called semiconductors.

Semiconductors conduct electricity with two types of carriers: holes and electrons

In a pure semiconductor, the number of electrons is equal to the number of holes. In a p-type semiconductor, the hole density is much greater than the electron density. In n-type semiconductors, the electron density is much greater than the hole density.

The n-p junction allows current to flow in one direction from p to n, which is called the rectification characteristic used to make semiconductor diodes. Semiconductors are also used to make transistors with current amplification properties.

=> Thus: Current in a semiconductor is the flow of conduction electrons moving in the opposite direction of the electric field and the flow of holes moving in the same direction as the electric field.

The effect of electric current

There are four main properties of electric current:

• The thermal (heating) effect of electric current

When current flows through a conductor, the temperature of the conductor increases, which is called the heating effect of the current.

Some appliances operate on the heating effect of electric current such as irons, light bulbs, water heaters, etc.

• The luminous effect of electric current

Electric current flows through the bulb causing the filament to heat up to a high temperature → making the bulb glow

• Magnetic effect of electric current

When current flows through a conductor, a magnetic field is created around the conductor, which is called the magnetic effect of the current.

Some devices operate on the operation of magnetic effect currents such as electric motors, electromagnets, etc.

• Chemical effects of electric current

In the experiment with copper sulfate salt solution, the phenomenon of copper being separated from copper salt solution when an electric current is passed proves that electric current has a chemical effect.

Effect of electric current on the human body

Positive impact

• Electricity reduces the excitability threshold of motor fibers
• Decreases sensory nerve responsiveness, thereby reducing pain
• Causes vasodilation in the body part between the 2 electrodes
• Increases the nutrient absorption capacity of the area where the current passes.
• Electric currents with appropriate intensity are widely used in medicine such as electro-acupuncture and acupuncture. In the case of cardiac arrest, the use of electric shock therapy can stimulate the heart to beat again to maintain life.

Negative impact

• 1 mA causes sharp pain.
• 5 mA causes a slight jerk.
• 50mA to 150 mA can be deadly, with effects such as rhabdomyolysis (muscle breakdown) or acute kidney failure (due to the release of toxins from broken muscle).
• 1mA to 4A causes arrhythmia and blood clotting..
• 10A causes cardiac arrest (household fuses usually trip at 10A).

Share 3 ways to check home electricity leakage

Method 1: Electric tester

Electrical testers are ideal for quickly checking equipment for leaks. Just place the tip of the test pen 1-2 cm away from the current without contacting the current. If there is electricity, the device will emit flashing lights so it is very safe.

Method 2: Check for electrical leakage with a multimeter

Many types of multimeters can measure leakage. With the easiest and most convenient operation, before starting to measure leakage current, make sure that you have a clear understanding of the measurement technique, parameters, and meaning on the multimeter.

1. First, connect the multimeter to the probe, put it in current mode and select the appropriate scale.
2. If you’re unsure of the range, it’s best to choose the highest range and then work your way down as you see fit. It will prevent copper from overloading.
3. Bring the probe to a point on the circuit and then read the result displayed on the screen.

Method 3: Use a clamp meter

Using a clamp meter to measure leakage current requires a certain understanding. Currently on the market there are many types of leakage current meters at low power levels.

What is electric current, amperage we have learned in the 7th grade physics program and 11th grade physics, the above article we have provided a lot of interesting and useful related knowledge. We believe that, with the above knowledge, you have a clear understanding of the characteristics, properties, and laws of electric current and are no longer confused when applying them to solving exercises related to this knowledge as well as There are safe ways to use electricity. Besides, you can learn some related knowledge such as what is the frequency of the current, what is the current transformer to expand the scope of knowledge.