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  • 电路电流控制

    Various electrical fuses displayed, used for controlling current in circuits.

    The amount of electric current that passes through a depends on the pushing the current and the opposing the flow of current. are designed for a specific voltage and resistance so that the current flow will be known. If the current is too large, the loss can damage the circuit, burn the resistors, or even burn the surrounding objects. Even with circuits designed to prevent such situations, accidents can happen, such as when wires touch each other unexpectedly. To prevent disasters, electrical circuits contain devices such as electrical fuses, circuit breakers, and surge protectors  to control the amount of current in the circuit. Examples of these devices are shown above, and explained below.
    ::通过电流的电流量取决于电流的推力和电流的对冲量。 电流是为特定电压和阻力设计的, 以便了解电流的流量。 如果电流过大, 电流会损坏电路, 烧掉阻力器, 甚至烧毁周围的物体。 即使使用旨在防止这种情况的电路, 事故也会发生, 比如电线意外地触碰对方。 为了防止灾难, 电路中含有电动引信、 断路器和电动保护器等装置, 以控制电流在电路中的数量 。 这些装置的例子见上文, 并解释如下 。

    Controlling Current in Electric Circuits
    ::电路电流控制

    In the wiring of a building, the wires carrying the current in and out are different and never touch directly. The charge passing through the circuit always passes through an appliance (which acts as a resistor) or through another resistor, which limits the amount of current that can flow through a circuit. Appliances are designed to keep current at a relatively low level for safety purposes. The appropriate voltage and resistance in a circuit keeps the current in control and keeps the circuit safe. It is possible, however, for something to happen that causes the wire bringing the current in to come into contact with either the wire carrying the current out or the ground wire, thus causing what is called a  short circuit . In a short circuit, some or all of the resistance is cut out of the circuit allowing the voltage to push a huge current through the wires.
    ::在建筑物的电线中,电流的电线是不同的,从不直接触动。电路通电总是通过电源(作为阻力器)或另一个阻力器,限制电流通过电路的流量。电源的设计是为了安全起见,将电流保持在相对较低的水平上。电路中的适当电压和阻力使电流保持控制并保持电路安全。但是,有可能发生某种情况,导致电流与电流的电线或地面电线发生接触,从而造成所谓的短路。在短路中,一些或全部阻力被切断,使得电流通过电线推出巨大的电流。

    For example, if a circuit has a potential difference of 100 volts and it is intended for the circuit to contain a 100 ohm resistance, then the wires carrying the current for this circuit will be designed for 1.0 amp. If that 100 ohm resistance is suddenly cut out of the circuit and only 0.10 ohm resistance remains, then the voltage will push 1000 amps of current through the circuit. This current overheats the wires and may damage the circuits or start a fire in the walls or the appliance. There are many possible causes of a short circuit, one possible cause could be something overheating, melting wires, and thereby fusing the circuit closed, bypassing the resistance.  Another cause might be something damaging the insulation of a wire, allowing the incoming and grounds wires to touch. In any case, once the resistance is lost, the voltage pushes a huge amount of charge through the wires causing them to overheat. 
    ::例如,如果电路可能存在100伏的差别,而且电路的电路可能含有100奥姆的阻力,那么该电路的电线将设计为1.0个阻力。如果100奥姆的阻力突然从电路中切断,只有0.10奥姆的阻力仍然存在,那么电压就会通过电路推动1000安培电流。这种电路过热,可能会破坏电路,或者在墙壁或电源中引发火灾。由于电路短路的许多原因,一个可能的原因是电路过热、融化电线,从而断电路,绕过阻力。另一个原因可能会破坏电线的隔热,允许电路进入和电线触碰。无论如何,一旦阻力丧失,电压就会通过电线大量电,导致电路过热。

    There are multiple ways to prevent these situations from occurring. The three most common protective devices are fuses, circuit breakers, and surge protectors.
    ::防止这种情况发生有多种办法。 三种最常见的保护装置是引信、断路器和激增保护装置。

    Fuses
    ::引信

    An electrical fuse is a device that sacrifices itself to provide over-current protection in an electrical circuit.
    ::电引信是一种装置,它牺牲了自己,在电路中提供外向保护。

    Conducting wires have a small electrical resistance. The electrical resistance of a conducting wire is related to the type of metal used and inversely related to the cross-sectional area of the wire. The larger the diameter of a wire, the greater the cross-sectional area, and the lower the electrical resistance will be. When electrons flow through a wire, they repel each other and interfere with the passage of other electrons. If there are a very large number of electrons passing through a wire with small diameter, the electrons will experience a greater resistance than if the wire diameter were larger and the electrons had more space between them.
    ::导电线的电阻力小于电阻力。导电线的电阻力与所使用的金属类型有关,反之与电线的横截面有关。线直径越大,横截面直径越大,电阻力就越低。当电子通过一条电线流动时,它们相互反射,并干扰其他电子的通过。如果有大量电子通过一条直径小的电线,电子的阻力就会大于线直径越大,电子之间的空间也越大。

    A glass electrical fuse with an internal wire designed to melt under excessive current.

    The image above is one type of electrical fuse . This fuse has a specially designed wire inside glass housing. The wire inside the glass is made of a particular metal and with a particular thickness to give the wire an exact resistance. This resistance will allow passage of normal current plus a marginal percentage more. If, however, the current exceeds the allowed value, the wire in the fuse will heat and melt, thus interrupting current flow through the circuit. The fuse wire is placed in the glass housing and a fuse mount to insulate the melting wire from its surroundings. Any unintended increase in current, such as short circuits, overloading, mismatched loads, or device failure will cause the fuse to burn out – protecting the other parts of the circuit from overheating and further damage.
    ::上面的图像是电动引信的一种类型。 引信在玻璃内有一个专门设计的电线。 玻璃内有一道专门设计的电线。 玻璃内有一条由特定金属组成的电线,并且有特定的厚度,使电线具有确切的阻力。 这种阻力将允许正常电流的通过,加上一个边际百分比。 但是,如果电流超过允许值,引信内的电线会热和熔化,从而中断电路的流。 引信线被放在玻璃内,一个引信塔,使熔化线与周围隔绝。 电流的任何意外增加,如短路、超载、不匹配的负荷或装置故障,都会导致引信燃烧 — 防止电路的其他部分过热和进一步损坏。

    This 'wire in glass' fuse is only one type of electrical fuse. Most fuses consist of a wire with small cross-sectional area compared to the circuit conductors, mounted between electrical terminals, and enclosed in a non-combustible housing. Regardless of the specific type of fuse, it is placed such that it carries all the current passing through the protected circuit. If the current flow gets too high, the fuse will melt. This destroys the fuse, but protects the remainder of the circuit.
    ::这种“玻璃电线”引信只是一种类型的电动引信。大多数引信由一条带小横截面的电线组成,与电路导线相比,这些电路导线安装在电终端之间,并被封闭在非可燃的舱内。不管引信的具体类型如何,引信都放置在它身上,将所有电流通过受保护的电路。如果电流过高,引信就会熔化。这摧毁了导线,但保护了电路的剩余部分。

    Circuit Breakers
    ::电路断路器

    The problem with fuses is they only work once. Every time you blow a fuse, you have to replace it with a new one. Like a fuse, a  circuit breaker  opens the circuit if the current reaches unsafe levels. Unlike a fuse, however, a circuit breaker can be used over and over again. The basic circuit breaker consists of a simple  switch , connected to an . The diagram below shows a typical basic circuit breaker design.
    ::引信的问题在于它们只能工作一次。 每次引爆引信,你必须用新的引信替换它。像引信一样,当电流达到不安全水平时,断路器打开电路。然而,与引信不同,断路器可以一次又一次地使用。基本的断路器由简单的开关组成,连接到一个 。下图显示典型的基本断路器设计。

    The Components And Operation Of A Basic Circuit Breaker.

    The red wire is the electrical circuit and is closed when the two contact points are connected.  When the switch is in the on position, electricity can flow through the red circuit, through the electromagnet, and out into the rest of the circuit.
    ::红线是电路,在两个联络点连接时关闭。当开关就位时,电能通过红电路、电磁网和电路的其余部分通电。

    The electricity magnetizes the electromagnet. Increasing the current boosts the electromagnet's magnetic force, while decreasing the current reduces the magnetic force. When the current reaches an unsafe level, the electromagnet's becomes strong enough to act on the soft iron bar, which is holding the left red wire in contact. When the soft iron bar is pulled down, the spring attached to the left red wire will lift the wire and break the circuit, causing the electricity to shut off. Once the circuit is broken, the electromagnet no longer emits a magnetic field, and the system can be reset by pushing the reset button. The reset button pushes the left red wire back in contact with the right red wire and also re-engages the soft iron bar that holds the contact in place.
    ::电能磁化电磁网。 增加电流会刺激电磁网的磁力, 同时减少电磁力。 当电磁网达到不安全水平时, 电磁网会变得足够强大, 足以在软铁棒上采取行动, 使左红线处于接触状态。 当软铁棒被拉倒时, 与左红线相连的弹簧会掀起电线, 并打破电路。 一旦电路破裂, 电磁网就不再发出磁场, 系统可以通过按下重置按钮重新设置。 重设按钮会将左红线与右红线连接, 并重新激活保持接触的软铁棒 。

    More advanced circuit breakers use electronic components (semiconductor devices) to monitor current levels rather than simple electrical devices. These elements are a lot more precise, and they shut down the circuit more quickly, but they are also a lot more expensive. For this reason, most houses still use conventional electric circuit breakers.
    ::更先进的断路器使用电子部件(半导体装置)来监测电流水平,而不是简单的电气装置。 这些元素更为精确,它们能更快地关闭电路,但成本也更高。 因此,大多数房屋仍然使用常规的断路器。

    When circuit breakers pop open due to excessive current, you do not have to replace the circuit breaker, you simply push a reset button. Of course, if the reason that the circuit breaker popped open is still present (like a short circuit), the circuit will simply pop open again when you reset it. When a circuit breaker pops open, you should determine the reason it opened and fix the problem before resetting the circuit breaker.
    ::当断路器因电流过大而打开时, 您不必替换断路器, 您只需按一个重置按钮即可。 当然, 如果断路器打开的原因仍然存在( 如短路) , 当重置时, 断路器会再次打开。 当断路器打开时, 您应该确定打开的原因, 并在重设断路器之前修正问题 。

    Surge Protection
    ::紧急保护

    A standard surge protector passes the electrical current along from the outlet to a number of electrical and electronic devices plugged into the power strip. If the voltage from the outlet surges or spikes (rises above the accepted level) the surge protector diverts the extra electricity into the outlet's grounding wire.
    ::标准增压保护装置将电流从出口传到连接到电力区的若干电气和电子装置。 如果出口电压溢出或加压(超过可接受的水平的升降),增压保护装置将额外的电流转移到出口的地面线上。

    The most common type of surge protector contains a component called a metal oxide varistor , or MOV , which diverts the extra voltage. As you can see in the diagram below, an MOV forms a connection between the hot power line and the grounding line.
    ::最常见的激增保护器类型包含一个称为金属氧化物变异体或MOV的部件,它转移了额外的电压。如下图所示,热电线和地面线之间有MOV连接。

    Diagram of a surge protector showing electrical connections and components like the MOV.

    An MOV has three parts: a piece of metal oxide material in the middle and two semiconductors that join it to the power and grounding lines. These semiconductors have a variable resistance that is dependent on voltage. When voltage is below a certain level, the electrons in the semiconductors flow in such a way as to create a very high resistance. When the voltage exceeds that level, the electrons behave differently, creating a much lower resistance. When the voltage is low, an MOV does nothing. When voltage is too high, an MOV can conduct a lot of current to the ground line, thus eliminating the extra voltage.
    ::MOV有三个部分:中间的一小块金属氧化物材料和连接到电线和地面线的两颗半导体。这些半导体具有取决于电压的可变抗力。当电压低于一定水平时,半导体中的电子会以产生极高抗力的方式流动。当电压超过这一水平时,电子会表现不同,产生低得多的抗力。当电压低时,MOV不会起作用。当电压太高时,MOV可以对地面线进行大量的电流,从而消除额外的电压。

    As soon as the extra current is diverted into the MOV and to ground, the voltage in the hot line returns to a normal level, causing the MOV's resistance to shoot up again. In this way, the MOV only diverts the surge current, while allowing the standard current to continue powering whatever machines are connected to the surge protector. Essentially, the MOV acts as a pressure release valve, only opening when the voltage exceeds set values.
    ::一旦额外的电流被转移到MOV和地面,热电线的电压就会恢复到正常水平,导致MOV的抵抗力再次冒出来。 这样,MOV只能改变激增的电流,同时允许标准电流继续驱动与增压保护装置连接的任何机器。 基本上,MOV起到压力释放阀的作用,只有在电压超过设定值时才打开。

    Have you ever wondered how the electricity in your house works? How can you turn the TV on without causing the lights in your living room to flicker or dim? How can the refrigerator stay on when the lights in the kitchen are off? Explore these questions and more in the Dollhouse simulation below:
    ::你有没有想过你家的电能如何运作?你怎么能在不造成客厅灯光闪烁或暗淡的情况下打开电视?当厨房的灯光熄灭时,冰箱怎么能保持?探讨这些问题,并在下面的Dollhouse模拟中更多地探讨这些问题:

    Further Reading
    ::继续阅读

    Summary
    ::摘要

    • An electrical fuse is a device that sacrifices itself to provide over-current protection in an electrical circuit.  If too much current flows, the fuse wire rises to a higher temperature and melts, thus opening the circuit, but destroying the fuse.
      ::电引信是一种在电路中牺牲自身以提供外向保护的装置。 如果电路流量过大,引信线会升至高温并熔化,从而打开电路,但会摧毁引信。
    • A circuit breaker opens a circuit as soon as the current climbs to unsafe levels, and can be used repeatedly.
      ::电路断路器一旦电流攀升到不安全水平,即打开电路,可以反复使用。
    • A standard surge protector passes a constant electrical current forward by diverting any extra electricity into a grounding wire.
      ::标准增压保护装置通过将任何额外的电源移入铺设电线,将固定电流传到前方。

    Review
    ::回顾

    1. As a wire conductor increases in diameter, the resistance ________________.
      1. increases
        ::增加数
      2. decreases
        ::减少
      3. stays the same
        ::保持原样
      4. changes color
        ::更改颜色

      ::随着导线导线直径增加,抗力增加 。 增量减少 保持相同的变化颜色
    2. The purpose of a fuse in an electrical circuit is to
      1. add another resistor
        ::添加另一个阻力器
      2. increase the circuit voltage
        ::增加电路电压
      3. limit the maximum current in the circuit
        ::限制电路中的最大电流
      4. none of these
        ::没有任何这些

      ::在电路电路中引信的目的是增加另一个阻力器,增加电路电压,限制电路的最大电流。
    3. What is the purpose of a circuit breaker in an electrical circuit?
      ::电路断路器的目的是什么?
    4. In some wire-in-glass fuses, the wire is not the same diameter all the way across the fuse. Many such fuses have one part of the wire that is considerably more narrow than the remainder of the wire. What is the purpose of this narrowing of the fuse wire?
      ::在一些玻璃管引信中,引信的直径与引信的直径不同,许多引信的一根线比引信的其余部分窄得多。

    Explore More
    ::探索更多

    Use this resource to answer the questions that follow.
    ::使用此资源回答下面的问题 。

     

    1. What happens to the fuse wire when the recommended current in a circuit is exceeded?
      ::当电路中建议的电流超过建议电流时,引信线会怎样?
    2. What is a common mistake made by homeowners when replacing burned fuses?
      ::房主在更换燃烧引信时犯了什么常见的错误?