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# 【速搜问答】什么是电阻

3年前 (2020-07-13) 599次浏览

Chinese-English Translation:

The resistance of a conductor to the current is called the resistance of the conductor. Resistance is a physical quantity, which indicates the size of the resistance of a conductor to current in physics. The greater the resistance of the conductor, the greater the resistance of the conductor to the current. Different conductors have different resistance. Resistance is a property of conductor itself.

The resistance of a conductor to the current is called the resistance of the conductor. Resistance (usually expressed by “R”) is a physical quantity, which indicates the resistance of a conductor to current in physics. The greater the resistance of the conductor, the greater the resistance of the conductor to the current. Different conductors have different resistance. Resistance is a property of conductor itself. The resistance of a conductor is usually represented by the letter R. the unit of resistance is Ohm, abbreviated as Ohm, and the symbol is Ω.

The current in a metal conductor is formed by the directional movement of free electrons. Free electrons frequently collide with positive metal ions in motion, and the number of collisions per second is about 1015. This kind of collision blocks the directional movement of free electrons, and the physical quantity indicating this blocking effect is called resistance. Not only metal conductors have resistance, but other objects also have resistance. The resistance of a conductor is determined by its physical conditions. The resistance of a metal conductor is determined by its material properties, length, thickness (cross-sectional area) and service temperature.

Resistor is called resistor directly in daily life. It is a current limiting element. After the resistor is connected to the circuit, the resistance value of the resistor is fixed. Generally, it has two pins, which can limit the current through the branch connected to it. A fixed resistor is called a fixed resistor. Variable resistance is called a potentiometer or variable resistor. The ideal resistor is linear, that is, the instantaneous current passing through the resistor is proportional to the applied instantaneous voltage. Variable resistor for voltage sharing. One or two movable metal contacts are pressed tightly on the bare resistor body. The contact position determines the resistance value between any end of the resistance body and the contact.

The terminal voltage and current have a definite functional relationship, reflecting the ability to convert electrical energy into other forms of two terminal devices, expressed by the letter R, in ohm Ω. Practical devices such as light bulb, heating wire and resistor can be expressed as resistor elements.

The resistance value of a resistance element is generally related to temperature, material, length and cross-sectional area. The physical quantity measuring the resistance affected by temperature is the temperature coefficient, which is defined as the percentage of resistance value change when the temperature increases by 1 ℃. The main physical characteristic of resistance is to change electrical energy into heat energy, which can also be said to be an energy consuming element. The current passing through it will produce internal energy. Resistance usually acts as voltage divider and shunt in the circuit. For signals, both AC and DC signals can pass through resistance.

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