Resistance (Resistance) is usually represented by "R"), which is a physical quantity that indicates the size of the conductor to the current obstacles in physics.The greater the resistance of the conductor, the greater the hindrance effect of the conductor on the current.Different conductors and resistors are generally different. Resistance is a characteristic of the conductor itself.The resistance will cause changes in electronic circulation. The smaller the resistance, the larger the electronic circulation, and vice versa.There is no resistance in the superconductor.
Photoresistance
The principle of the optical resistance working principle internal photoelectric effect, the principle of optical resistance working is based on it.When the range of a certain wavelength is irradiated into the light -sensitive resistance, the current in the circuit increases rapidly, and its resistance value decreases sharply. At this time, the sensitivity of the light -sensitive resistance is high. Generally speakingThe larger the dark resistance, the better it is. The dark electricity value of the light -sensitive resistance is generally more than thousands of Euros or more in the Zhaou -Europe level and bright resistance.
Resistivity
1. Overview resistivity is a physical quantity used to represent various material resistance characteristics.The length of 1 meter and cross -sectional area made of a certain material is the resistivity of the wire of the wire at normal temperature (20 ° C) at normal temperature (20 ° C), called the resistivity of this material.The resistivity is not related to factors such as the length of the conductor, the cross -sectional area and other factors. It is the electrical properties of the conductor material itself. It is determined by the material of the conductor and is related to temperature.The unit of resistance in the international unit system is ω · m, read as Ommi, referred to as Omi.The commonly used unit is "Ohm centimeters".2. In the international unit system, the unit of resistivity is Omm (ω · m or OHMM), and the commonly used units are Ommmm and Ohmm.3. The calculation formula of the calculation formula resistivity is: ρ = RS/Lρ is the resistivity -commonly used unit ω · ms is the cross -sectional area -common unit iconic R is the resistance value -commonly used unit ωl is the length of the lead -Commonly used units m -------------------------------------------------------- another calculation of resistance to resistivityThe formula is: ρ = E/Jρ is the resistivity -commonly used unit ω · mm2/m [1] E is the strength of the electric field -common unit N/CJ is current density —Vector)
Resistance formula
1. Calculate formula: R = R1+R2+...+Rn.Parallel: 1/r = 1/r1+1/r2+1/r3+...+1/rn, specially, the two resistors can also be expressed as R = R1XR2/R1+R2.Definition: R = U/I Decisive formula: R = ρL/s (ρ indicates the resistivity of the resistance, which is determined by its own nature. L represents the length of the resistance and s represents the cross -sectional area of ??the resistor).Second, the unit represents the resistance of the conductor is usually expressed in the letter R. The unit of the resistor is Om (OHM), referred to as Europe, the symbol is ω (Greek letters, read as omega), 1Ω = 1V/a.The relatively large units include thousands of Euros (KΩ), Zhaou (mΩ) (MR = million, that is, 1 million).KΩ (Thousand Our), MΩ (Zhaou), their conversion relationship is: two resistors parallel formula can also be expressed as 1tΩ = 1000gΩ; 1gΩ = 1000mΩ; 1mΩ = 1000kΩ; 1kΩ = 1000Ω (that is, one thousand advance rates)
Resistance
I. The current limitation of the resistance is not exceeded that the current of the electrical appliance does not exceed the rated value or the required value of the actual work to ensure the normal work of the electrical appliances. It can usually connect a variable resistor in the circuit.When the size of this resistance is changed, the size of the current also changes.We call this resistance that can limit the size of the current as a current -limiting resistor.Second, the voltage of the resistance is generally marked with the rated voltage value on the electrical appliance. If the power supply is high than the rated voltage of the electrical appliance, the electrical appliance cannot be directly connected to the power supply.In this case, an appliances can be connected to an appropriate resistance value with electrical appliances, allowing it to share a part of the voltage, and the electrical appliance can work under the rated voltage.We call this resistance as a separate pressure resistance.Third, when the resistance is converted into the actual energy of the internal energy through the resistance, the electrical energy will be converted into the entire energy.Used an electrical appliance for transforming electrical energy as an electric heater.Such as electric soldering iron, electric furnace, rice cooker, heater, etc.
Dorgery measurement
1. Overview the purpose of using the current meter and voltage expression to the specific resistance value of the measurement resistance.伏安法测电阻(具体分为“电流表外接法”和“电流表内接法”)原理：欧姆定律(R=U/I)二、用万用表测电阻方法/步骤1、首先是直接测量电阻，Lets talk about the traditional multimeter first.Put the pointer to the gear shown in the figure (Ohm ω). This is the gear of the measurement of the resistance.2. The starting position of the current and voltage reading 0 is on the left, and the starting position of the resistor 0 finds the read number of the resistance on the right.3. Docking the two pens of the multimeter and then see if the pointer points to the 0 position.If it is not a place where the multimeter has a mechanical adjustment, rotate it to zero it (if 0 cannot be adjusted 0 indicates that the battery is out of power)

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