20.8 抵抗
Section outline
-
These athletes are playing rugby, a game that is similar to American football. The players in red and blue are trying to stop the player in blue and black from running across the field with the ball. They are resisting his forward motion. This example of resistance in rugby is a little like resistance in physics .
::这些运动员正在玩橄榄球,这个游戏与美国足球类似。 红蓝球运动员试图阻止蓝黑色球员与球一起横跨球场。他们抵制球员的前进运动。橄榄球中的抵抗例子有点像物理学中的抵抗。What Is Resistance?
::什么是抵抗组织?In physics, resistance is opposition to the flow of electric charges in an electric current as it travels through matter. The SI unit for resistance is the ohm. Resistance occurs because moving electrons in current bump into atoms of matter. Resistance reduces the amount of electrical energy that is transferred through matter. That’s because some of the electrical energy is absorbed by the atoms and changed to other forms of , such as .
::在物理学中,抗力是反对电流中电流随物质流动而流动的电源。 SI的抗力单位是ohm。 抗力之所以发生,是因为在电流碰撞到原子的物质中移动电子。 抗力减少了通过物质传输的电能量。 这是因为部分电能被原子吸收并改变为其他形式的能源,比如:Q: In the rugby analogy to resistance in physics, what do the players on each team represent?
::问:在橄榄球类比物理学抵抗力的类比中,每个球队的球员代表什么?A: The player on the blue and black team represents a moving in an electric current. The players on the red and blue team represent particles of matter through which the current is flowing.
::A: 蓝色和黑色球队的玩家代表着电流的移动。 红色和蓝色球队的玩家代表着电流流通过的物质粒子。Factors That Affect Resistance
::影响抵抗力量的因素How much resistance a material has depends on several factors: the type of material, its width, its length, and its .
::材料的耐药性有多大取决于几个因素:材料的类型、其宽度、其长度和其耐药性。-
All materials have some resistance, but certain materials resist the flow of electric current more or less than other materials do. Materials such as plastics have high resistance to electric current. They are called electric insulators. Materials such as
have low resistance to electric current. They are called electric conductors.
::所有材料都有一定的阻力,但某些材料比其他材料多或少地抵制电流流动,塑料等材料对电流有很强的阻力,称为电解器,对电流的阻力较小,称为电导器。 -
A wide wire has less resistance than a narrow wire of the same material. Electricity flowing through a wire is like water flowing through a hose. More water can flow through a wide hose than a narrow hose. In a similar way, more current can flow through a wide wire than a narrow wire.
::一条宽线的阻力小于同一材料的窄线。 通过一条电线输送的电力就像通过一条水管流水一样。 更多的水能通过一条宽水管流过一条宽水管,而不是窄水管。 类似地,流能通过一条宽线流得比窄线流得大。 -
A longer wire has more resistance than a shorter wire. Current must travel farther through a longer wire, so there are more chances for it to collide with particles of matter.
::更长的铁丝网比短的铁丝网的阻力更大。 电流必须经过更长的铁丝网,因此它更有可能与物质粒子相撞。 -
A cooler wire has less resistance than a warmer wire. Cooler particles have less
, so they move more slowly. Therefore, they are less likely to collide with moving electrons in current. Materials called superconductors have virtually no resistance when they are cooled to extremely low temperatures.
::冷却线的阻力比暖和线的阻力要小。 冷却粒子的阻力要小一些,因此移动速度要慢一些。 因此,它们不太可能与流动电流中的电子相撞。 当它们被冷却到极低的温度时,被称为超导体的材料几乎没有抵抗力。
Is Resistance Good or Bad?
::抵抗是好还是坏?Resistance can be helpful or just a drain on electrical energy. If the aim is to transmit electric current through a wire from one place to another, then resistance is a drawback. It reduces the amount of electrical energy that is transmitted because some of the current is absorbed by particles of matter. On the other hand, if the aim is to use electricity to produce heat or light, then resistance is useful. When particles of matter absorb electrical energy, they change it to heat or light. For example, when electric current flows through the tungsten wire inside an incandescent light bulb like the one in the Figure , the tungsten resists the flow of electric charge . It absorbs electrical energy and converts some of it to light and heat.
::抗力可以起到帮助作用, 或者仅仅是电能的耗竭。 如果目的是通过电线将电流从一个地方传送到另一个地方,那么抵抗就是一种缺陷。 它会减少因某些电流被物质粒子吸收而传播的电能数量。 另一方面, 如果目的是用电来产生热或光,那么抗力是有用的。 当物质粒子吸收了电能时, 它们会将其改变为热或光。 例如, 当电流通过像图中那样的白喉灯泡的通电线流动时, 会阻抗电源的流。 它会吸收电能, 并将一部分电能转换成光和热。What’s wrong with this picture? (Hint: How does current get to the light bulb?)
::这张照片有什么问题? (提示:电流如何到达灯泡? )Q: The tungsten wire inside a light bulb is extremely thin. How does this help it do its job?
::问题:灯泡里面的线非常薄。这如何帮助它完成任务?A: The extremely thin wire has more resistance than a wider wire would. This helps the wire resist electric current and change it to light.
::A: 极薄的铁丝网的阻力大于较宽的铁丝网的阻力。 这有助于铁丝网抵抗电流,将其变为光线。Summary
::摘要-
In physics, resistance is opposition to the flow of electric charges that occurs as electric current travels through matter. The SI unit for resistance is the ohm.
::在物理学中,抵抗是反对电流电费的流动,电流随着电流通过物质流动而出现电费的流动。 -
All materials have resistance. How much resistance a material has depends on the type of material, its width, its length, and its temperature.
::所有材料都具有抵抗力。一种材料的抵抗力取决于材料的类型、宽度、长度和温度。 -
Resistance is a hindrance when a material is being used to transmit electric current. Resistance is helpful when a material is being used to produce heat or light.
::当材料被用于输送电流时,抵抗是一种障碍,当材料被用于产生热或光时,抵抗是有用的。
Review
::回顾-
What is resistance? Name the SI unit for resistance.
::抵抗是什么? -
Explain what causes resistance.
::解释是什么导致抵抗。 -
Describe properties of a metal wire that would minimize its resistance to electric current.
::描述金属线的特性,以尽量减少其对电流的抗力。 -
Extend the rugby analogy to explain why a longer wire has greater resistance to electric current.
::扩大橄榄球类比,解释为什么长线对电流的抵抗力更大。 -
Copper wires have about one-third the resistance of tungsten wires. Why would copper be less suitable than tungsten as a filament in an incandescent light bulb?
::铜线的抗力大约是钨线的三分之一。 为什么铜比钨线更不适合作为白白灯泡中的丝质呢?
-
All materials have some resistance, but certain materials resist the flow of electric current more or less than other materials do. Materials such as plastics have high resistance to electric current. They are called electric insulators. Materials such as
have low resistance to electric current. They are called electric conductors.
