What is the relationship between the magnitude of the resistance and the material

The size of the resistance has nothing to do with the material in general, and the chip type is mainly in terms of power and current

The material is the biggest factor in determining the magnitude of the resistance.

The resistance of the object r= l s

In the above equation, r is the resistance value – the commonly used unit

is resistivity – the common unit ·m

s is the cross-sectional area – a commonly used unit

l is the length of the wire - the common unit m

Resistivity is a physical quantity used to express the electrical properties of various substances. It depends on the properties of the material.

The resistivity of a wire made of a material with a length of 1 meter and a cross-sectional area of 1 square millimeter at room temperature (20 hours) is called the resistivity of this material. The unit of resistivity is the ohm-meter (·m or ohmm), and the common units are the ohm-millimeter and the ohm-meter.

Other than that. 1 Resistivity is not only related to the material of the conductor, but also to the temperature of the conductor. In the range where the temperature does not change much:

The resistivity of almost all metals varies linearly with temperature, i.e. = o(1+at). where t is the temperature in Celsius, o is the resistivity at o, and a is the temperature coefficient of resistivity.

2 Since resistivity changes with temperature, the physical state in which some electrical appliances are resisted must be stated. For example, the resistance of a 220 V -100 W electric light filament is 484 ohms when energized, and only about 40 ohms when unenergized.

3 Resistivity and resistance are two different concepts. Resistivity is a property that reflects the effect of a substance on the resistance of an electric current, and resistance is a property that reflects the effect of an object on the resistance of an electric current. See.

When the voltage at both ends of the conductor is constant, the current flowing through the conductor is inversely proportional to the conductor resistance.

The formula for the relationship between current, voltage and resistance is: i=u r, where i is current, u is voltage, and r is resistance. From the above formula, it can be seen that when the voltage is constant, the larger the current, the smaller the resistance, and vice versa, the smaller the current, the greater the resistance.

Resistance is a property of the conductor itself, so the resistance of the conductor has nothing to do with factors such as whether the conductor is connected to the circuit, whether there is current in the conductor, and the magnitude of the current. The resistivity of a superconductor is zero, so the resistance of a superconductor is zero.

There are many kinds of resistor materials, and the common resistor materials are as follows:

1.Carbon materials: Carbon materials include graphite, activated carbon, bulk carbon, etc., which are often used to manufacture high-precision and low-noise resistors.

2.Metal materials: Metal materials such as iron, copper, chromium, nickel, tungsten, etc., are mainly used to manufacture high-power resistors, with good electrical conductivity and thermal conductivity.

3.Ceramic materials: Ceramic materials are resistant to high temperatures and corrosion, and are commonly used in the manufacture of high-precision fixed resistors and potentiometers.

4.Semiconductor materials: Semiconductor materials such as silicon, germanium, etc., are often used in the manufacture of voltage regulators and temperature sensors.

5.Clay materials: Clay materials include carbon clay, corona ceramics, porcelain bottle halo clay, etc., which are commonly used in the manufacture of high-voltage resistors.

The above are common resistive materials, each of which has its own characteristics and scope of application. Different circuit applications require different resistor materials.

1. The resistor is generally made of metal materials, such as metal alloys, because the resistance of metal alloys does not change much with temperature, while thermistors are generally made of semiconductor materials, because the resistance value of semiconductors changes significantly with temperature, and there are some other materials.

2. The resistance of the conductor to the current is called the resistance of the conductor. Resistance (commonly represented by "R" in Tongshisen) is a physical quantity, which in physics indicates the magnitude of the resistance of a conductor to an electric current. The greater the electrical deficit of the conductor, the greater the resistance of the conductor to the current.

The magnitude of the resistance is related to the material, length, cross-sectional area, and temperature of the conductor.

When the material and cross-sectional area are the same, the longer the length of the conductor, the greater the resistance.

When the material and length are the same, the smaller the cross-sectional area of the conductor, the greater the resistance. When the length and cross-sectional area are the same, the conductor resistance of different materials is different.

For most conductors, the higher the temperature, the greater the resistance, such as metals, etc.; For a few conductors, the higher the temperature, the lower the resistance, such as carbon.

Resistance is a physical quantity that in physics indicates the magnitude of a conductor's action on the resistance of an electric current. The greater the resistance of a conductor, the greater the resistance of the conductor to the current. Different conductors, the resistance is generally different, and resistance is a property of the conductor itself.

The resistance of a conductor is usually denoted by the letter r, and the unit of resistance is ohms.

Question 1: What factors are related to the magnitude of the resistance Answer: The magnitude of the resistance of a metal conductor is related to the resistivity, length, cross-sectional area, and temperature of the conductor.

According to the law of resistance r= l s

1. The greater the resistivity, the larger the length, the smaller the cross-sectional area, the greater the resistance of the conductor, the higher the temperature increases, the resistivity of the metal conductor increases, and the resistance increases.

2. When the temperature of the conductor drops to a certain temperature, the resistance of the conductor suddenly drops to 0, which is called superconductivity.

3. Thermistile resistance to semiconductors: When the semiconductor is heated, the resistance decreases rapidly with the increase of temperature, and it responds quickly to small temperature changes with high accuracy.

4. For AC circuits, inductance coils, inductance xl=2 fl, capacitance xc=1 2 fc

Question 2: Why is the length of the resistor related to the size of the resistance The relationship between the length of the resistance and the size of the resistance is as follows:

1 It is related to the resistivity of the material. Every type of conductor has its resistivity. The higher the value, the greater the resistance.

2 It is related to the cross-sectional area of the conductor, the smaller the cross-sectional area, the greater the resistance. 3 It is related to the temperature of the conductor, the higher the temperature, the greater the resistance. 4 It is related to the length, the longer the length, the greater the resistance.

The results of the experiments passed: the resistance value of the wire of different materials of the same length and the same cross-sectional area is not equal The cross-sectional area is unchanged, and the resistance value of the wire of the same material is proportional to the length The length is unchanged, and the resistance value of the wire of the same material is inversely proportional to the size of the cross-sectional area.

The law of resistance is summarized: (1) Content: The resistance r of a conductor of the same material is proportional to its length l and inversely proportional to its cross-sectional area s; The conductor electrical group is related to the materials that make it up.

This is the law of resistance. (2) Formula: r=

where l s is the proportionality constant, which is related to the material of the conductor and is a physical quantity that reflects the conductive properties of the material, which is called the resistivity of the material.

Generally speaking, the volume of the resistor is related to the power, and the higher the power, the larger the volume.

There are the following exceptions:

1. The resistors made of different materials or processes cannot judge the power according to the volume. For example, a metal film resistor of the same volume is more than twice as powerful as a carbon film resistor.

2. The volume of variable resistance and fine-tuning resistance mainly depends on whether it is convenient to adjust the resistance value, and it may not be related to power.

It's mostly about power. The greater the resistance, the smaller the current passing through and the smaller the power; The smaller the resistance value, the greater the current passing through, the greater the power, the more obvious the heating, and the easier it is to burn out the resistor. And the larger the volume, the easier it is to dissipate heat.

Do you understand the relationship between resistance, volume, and power?

The magnitude of the resistance value is generally related to the length, cross-sectional area, material, and temperature.

When the material and cross-sectional area are the same, the longer the length of the conductor, the greater the resistance. When the material and length are the same, the smaller the cross-sectional area of the conductor, the greater the resistance. When the length and cross-sectional area are the same, the conductor resistance of different materials is different.

For most conductors, the higher the temperature, the greater the resistance; For a small number of conductors, the higher the temperature, the lower the resistance. Resistance is a property of the conductor itself, so the resistance of the conductor has nothing to do with factors such as whether the conductor is connected to the circuit, whether there is current in the conductor, and the magnitude of the current. The resistivity of a superconductor is zero, so the resistance of a superconductor is zero.

1. Carbon film resistance: gaseous hydrocarbons decompose at high temperature and vacuum, and the carbon is deposited on the porcelain rod and porcelain tube to form a crystalline carbon film. Different resistance values can be obtained by changing the thickness of the carbon film and changing the length of the carbon film by the method of notching. Low cost and average performance.

2. Metal film resistance: the alloy is heated in a vacuum, and the alloy evaporates to form a layer of conductive metal film on the surface of the porcelain rod. Notching or changing the thickness of the metal film can control the resistance. Compared with carbon film resistors, this kind of resistance is small in size, low in noise, and has good stability, but the cost is high.

3. Carbon resistance: carbon black, resin, clay and other mixtures are pressed and then made by heat treatment. A color ring is used on a resistor to indicate its resistance value. This kind of resistor has a low cost and a wide range of resistance values, but its performance is poor and it is rarely used.

4. Wire-wound resistance: It is made of constantan or nickel-chromium alloy resistance wire wound on the ceramic skeleton. There are two types of resistance: fixed and variable. It is characterized by stable work, good heat resistance, small error range, suitable for high-power occasions, and the rated power is generally more than 1W.