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  • 电路

    Lesson Objectives
    ::经验教训目标

    • Identify the parts of an electric circuit.
      ::标明电路的部件。
    • Identify electric safety features and how to use electricity safely.
      ::查明电力安全特征和如何安全使用电力。

    Lesson Vocabulary
    ::词汇表课程

    • electric circuit
      ::电电电电线路

    Introduction
    ::导言

    Look at the battery and light bulb in  Figure  . We know the light bulb works, but it won’t light. Why? It’s connected to a battery. What is the problem? The problem is the loose wire on the left. It must be connected to the battery. If not, the bulb will not light up. What is the reason? Electric current can flow through a material only if the material forms a closed loop. Electricity must have an unbroken path to follow.
    ::看看图中的电池和灯泡。我们知道灯泡起作用了,但是它不会亮。为什么?它和电池连接在一起。有什么问题?问题是左侧的松线。它必须连接到电池上。如果没有,灯泡就不会亮起来。原因是什么?电流只有在材料形成闭环时才能通过材料流动。电力必须有一个不断的路径。

    lesson content
     
    Electric current cannot flow through an open circuit.

    Parts of an Electric Circuit
    ::电路部件

    All electric circuits have at least two parts: a voltage source and a conductor.
    ::所有电路至少有两部分:电压源和导电器。

    The voltage source of the circuit in  Figure   is a battery. You have previously learned about potential energy. In other words, something may have the potential to cause change. Voltage is the potential that causes the current to flow. It would be like the cliff the boulder is sitting on. The battery does not supply the current. Instead it supplies the potential. In a home circuit, the voltage source may be a nearby electric power plant. This local power plant may supply electricity to many homes. 
    ::图中的电路电压源是一个电池。 您以前已经了解过潜在的能量。 换句话说, 电压是可能导致电流变化的潜能。 电压是导致电流的潜能。 电压是巨石悬崖, 电池不能提供电流。 相反, 电压源提供电流。 在家电路中, 电压源可能是附近的电厂。 这个本地电厂可以向许多家庭供电 。

    The conductor in most circuits consists of one or more wires. Conductors are materials that allow the flow of electricity through them. The conductor must form a closed loop. This loop runs from the source of voltage and back again. In  Figure   , the wires are connected to both terminals of the battery. They form a closed loop. There must be a closed loop for electricity to flow. 
    ::大多数电路的导体由一个或多个电线组成。导体是允许电流通过电源的材料。导体必须形成一个闭路环。该环从电压源和回路循环。在图 中,电线与电池的两个终端连接,形成一个闭路环。电流必须有一个闭路环。

    lesson content
     
    A circuit must be closed for electric devices such as light bulbs to work. The arrows in the diagram show the direction in which electrons flow through the circuit. The current is considered to flow in the opposite direction.

    The circuit in  Figure   also has two other parts. There is a light bulb and a switch. 
    ::图中的电路还有另外两个部分,有一个灯泡和一个开关。

    • Most circuits contain some type of device. This device converts electric energy to other forms of energy. In your home you may have a device called a light bulb. A light bulb converts electricity into light and heat. What other types of devices do you have in your home? What does it convert electricity into? 
      ::大多数电路都包含某种类型的设备。 这个设备可以将电能转换为其他形式的能源。 在您的家中, 您可能拥有一个叫做灯泡的装置。 一个灯泡可以将电力转换为光和热。 您家里还有什么其他类型的设备? 它将电能转换成什么 ?
    • Many circuits have switches. Switches control the flow of current through the circuit. When the switch is turned on, the circuit is closed. When the switch is closed the electricity can flow. When the switch is turned off, the circuit is open. Open circuits do not allow a current to pass through them. 
      ::许多电路都有开关。 开关控制电流通过电路的流。 当开关打开时, 电路被关闭。 当开关关闭时, 电路可以流动。 当开关关闭时, 电路被打开。 打开电路不允许电流通过电路 。

    Electric Safety
    ::电气安全

    Electricity is dangerous. Contact with electric current can cause severe burns and even death. Electricity can also cause serious fires. A common cause of electric hazards and fires is a short circuit. 
    ::与电流接触可造成严重烧伤甚至死亡,电力也可造成严重火灾,电危害和火灾的一个常见原因是电路短路。

    How a Short Circuit Occurs
    ::如何短电路操作

    An electric cord contains two wires. One wire carries current from the outlet to some electrical device. The other wire carries current back to the outlet. Did you ever see an old appliance with a damaged cord, like the one in  Figure  ? A damaged electric cord can cause a severe shock. Damaged cords can allow current to pass from the cord to a person who touches it. A damaged cord can also cause a short circuit. A short circuit occurs when electric current follows a shorter path than is intended. For example, if the two wires in a damaged cord come into contact with each other, current flows from one wire to the other. The current will bypass the appliance and take the easiest route. This may cause the wires to overheat and start a fire.
    ::电线包含两条电线。 一条电线将电流从出口输送到一些电装置。 另一条电线将电流输送到出口。 您有没有看到过一条旧的电源, 带损坏的电线, 像图中的电线那样? 受损的电线可能会造成严重震荡。 损坏的电线可以让电流从电线传到触电线的人身上。 受损的电线也可以造成短路。 当电流沿着比预想的更短的路径运行时, 就会发生短路。 例如, 被损坏的电线中的两条电线相互接触时, 电流会从一条电线传到另一条电线。 电流会绕过电源, 绕过最容易的线路。 这可能导致电线过热而起火 。

    lesson content
     
    A damaged electric cord is a serious hazard. How can it cause an electric short?

    Electric Safety Features
    ::电气安全特点

    Electricity can be very dangerous. To reduce the risk of injury, safety features are built into electric circuits and devices. You might have noticed some of these in your home. They include three-prong plugs, circuit breakers, and GFCI outlets. Each feature is described and illustrated in  Table  . 
    ::为了降低受伤风险,电路和装置中安装了安全功能。你可能已经注意到了家中的一些安全特征,包括三根插头、断路器和GFCI入口。每个特征在表格中说明和说明。

    Can you find one or more examples of these electric safety features in your home?
    Electric Safety Feature Description

    Three-Prong Plug
    ::三项目插件

    lesson content
     

    		 A three-prong plug is generally used on metal appliances. The two flat prongs carry the current. The round prong is for safety. It connects with a wire inside the outlet. This wire connects to the ground. By redirecting the current it can pass into the ground. The ground is where it can be harmlessly absorbed.

    Circuit Breaker
    ::电路断路器

    lesson content
     

    		 A circuit breaker is another safety feature. The circuit breaker automatically opens a circuit if too much current flows through it. This could happen if too many electric devices are plugged in. It can also happen if there is an electric short. Once the problem is resolved, the circuit breaker can be switched back on. Once switched back on, the circuit is closed. Once closed, the current can once again flow. Circuit breakers are generally found in a breaker box. This box controls all the circuits in a building. 

    GFCI Outlet
    ::GFCI 输出

    lesson content
     

    		 GFCI stands for ground-fault circuit interrupter. GFCI outlets are typically found in bathrooms and kitchens. They are used where water may pose a risk of shock. Water is a good electric conductor. A GFCI outlet contains a special device. The device monitors the amounts of current leaving and returning to the outlet. If less current is returning than leaving, this means that current is escaping. When this occurs, a tiny circuit breaker in the outlet opens the circuit. The breaker can be reset by pushing a button on the outlet cover.  

     

     

    Using Electricity Safely
    ::安全使用电力

    Even with electric safety features, electricity is still dangerous. It must be used safely. Follow the safety rules below to reduce the risk of injury or fire from electricity.
    ::即便有电能安全功能,电仍很危险,必须安全使用,遵守以下安全规则,降低电伤或火灾的风险。

    • Never mix electricity and water. Don’t turn on or plug in electric lights or appliances when your hands are wet. Do not turn on switches if you are standing in water, or you are in the shower or bathtub. The current could flow through the water—and you. Remember, water is a very good electric conductor.
      ::永远不要混合电力和水。 手湿的时候,不要打开或插上电灯或电器。 站在水里或淋浴或浴缸里的人,不要打开开关。 水流会流过水,而你也会流过水。 记住,水是一个很好的电导器。
    • Never overload circuits. Avoid plugging too many devices into one outlet or extension cord. The more devices that are plugged in, the more current the circuit carries. Too much current can overheat a circuit and start a fire.
      ::永远不要超载电路。 避免将太多的设备插入一个出口或延伸线。 插入的装置越多, 电路随波越长。 太多的电流会过热, 导致电路起火 。
    • Never use devices with damaged cords or plugs. They can cause shocks, shorts, and fires.
      ::永远不要使用有损坏的绳索或插头的装置,它们可能造成冲击、短裤和火灾。
    • Never put anything except plugs into electric outlets. Plugging in other objects is likely to cause a serious shock that could be fatal.
      ::除了电源插座之外,从来没有设置过任何插座。 插插其他物体可能会造成严重冲击,造成致命的冲击。
    • Never go near fallen electric lines. They could be carrying a lot of current. Report fallen lines to the electric company as soon as possible.
      ::永远不要靠近倒塌的电线。 他们可能携带大量电流。 尽快向电力公司报告电线下降的情况。

    Lesson Summary
    ::经验教训摘要

    • An electric circuit is a closed loop. The closed loop allows electric current to flow through it. A circuit must include a voltage source. It also needs to have a conductor. Conductors are usually wires that carry the current. The current flows from the voltage source and back again.  Circuits usually contain devices that convert electricity into other useful forms.
      ::电路是一个闭路回路。 闭路回路允许电流通过电流。 电路必须包含电压源。 电路还必须有一个电源。 导电器通常是电流的电线。 电源的电流和电源的回流。 电路通常包含将电力转换为其他有用形式的设备。
    • Electricity is dangerous. Electric shorts can even start fires. Electric safety features include three-prong plugs, circuit breakers, and GFCI outlets. Even with electric safety features, it’s important to use electricity safely.
      ::电力是危险的。 电短裤甚至可以起火。 电安全功能包括三根插头、断路器和GFCI插座。 即使有电安全功能,安全使用电力也很重要。

    Lesson Review Questions
    ::经验回顾问题

    Recall
    ::回顾

    1. Identify the parts of an electric circuit.
      ::标明电路的部件。
    1. Identify an electric safety feature and describe how it works.
      ::确定电能安全特征,并描述其运作方式。
    1. List three tips to reduce the risk of injury or fire from electricity.
      ::列出减少电伤或火灾风险的三点提示。

    Apply Concepts
    ::应用概念

    1. Draw a simple electric circuit that includes a battery, light bulb, and switch. Use arrows to show the flow of electrons through the circuit.
      ::绘制简单的电路, 包括电池、 灯泡和开关。 使用箭头显示电路中的电子流 。

    Think Critically
    ::仔细仔细思考

    1. Explain how a short circuit occurs.
      ::解释一下短路是如何发生的

    Points to Consider
    ::需要考虑的要点

    In this lesson, you read that electric devices convert electrical energy to other forms of energy. For example, a microwave oven converts electrical energy to electromagnetic energy in the form of microwaves. A blender converts electrical energy to sound energy and the kinetic energy of the whirring blades.
    ::在这一课中,你读到,电动装置将电能转换成其他形式的能源。例如,微波炉将电能转换成微波形式的电磁能。搅拌器将电能转换成声音能量和电动能量,而电动电动能量则由电动电动刀片转换成电动能量。

    • Do you think all electric devices convert electrical energy to other forms of energy?
      ::你认为所有电动装置 都把电能转换成其他能源吗?
    • Computers are familiar electric devices. Do you know how they use electric current?
      ::电脑是熟悉的电动装置 你知道他们怎么用电流吗?