4.4 电路
Section outline
-
Electric Circuit Basics
::电路基本基本电路Akshit made this sketch of a battery and light bulb for science class. If this were a real set up, the light bulb wouldn’t work. The problem is the loose wire on the left. It must be connected to the positive terminal of the battery in order for the bulb to light up.
::Akshit为科学课绘制了电池和灯泡的草图。 如果这是真的装置,灯泡是行不通的。 问题是左侧的松线。 它必须连接到电池的正终端,以便灯泡亮起来。A closed loop through which current can flow is called an electric circuit .
::水流流的闭路环叫做电路。Parts of an Electric Circuit
::电路部件All electric circuits have at least two parts: a voltage source and a conductor. They may have other parts as well, such as light bulbs and switches, as in the simple circuit seen in the Figure .
::所有电路至少有两部分:电压源和导电器,还可能有其他部件,如灯泡和开关,如图3所示的简单电路。-
The voltage source of this simple circuit is a battery. In a home circuit, the source of voltage is an electric power plant, which may supply electric current to many homes and businesses in a community or even to many communities.
::这种简单电路的电压来源是电池,在家庭电路中,电压来源是电厂,电厂可为社区甚至许多社区的许多家庭和企业提供电流。 -
The conductor in most circuits consists of one or more wires. The conductor must form a closed loop from the source of voltage and back again. In the circuit above, the wires are connected to both terminals of the battery, so they form a closed loop.
::大多数电路的导体由一个或多个电线组成。导体必须从电压源形成一个闭路循环,然后从电压源和回路形成一个闭路循环。在以上电路中,电线与电池的两个终端连接,从而形成一个闭路循环。 -
Most circuits have devices such as light bulbs that convert electrical energy to other forms of energy. In the case of a light bulb, electrical energy is converted to light and thermal energy.
::大多数电路都有灯泡等装置,将电能转换成其他形式的能源,就灯泡而言,电能转换成光能和热能。 -
Many circuits have switches to control the flow of current. When the switch is turned on, the circuit is closed and current can flow through it. When the switch is turned off, the circuit is open and current cannot flow through it.
::许多电路都有控制电流流动的开关。 当开关打开时, 电路是封闭的, 电路可以流过电路。 当开关关闭时, 电路是开放的, 电路不能流过电路 。
Circuit Diagrams
::电路图图When a contractor builds a new home, she uses a set of plans called blueprints that show her how to build the house. The blueprints include circuit diagrams. The diagrams show how the wiring and other electrical components are to be installed in order to supply current to appliances, lights, and other electric devices. You can see an example of a very simple circuit in the Figure . Different parts of the circuit are represented by standard circuit symbols. An ammeter measures the flow of current through the circuit, and a voltmeter measures the voltage. A resistor is any device that converts some of the electricity to other forms of energy. For example, a resistor might be a light bulb or doorbell.
::当承包商建造新房子时,她使用一套称为蓝图的计划,显示她如何建造房子。蓝图包括电路图。图表显示如何安装电线和其他电气部件,以便向电器、灯和其他电动装置提供电流。图中可以看到一个非常简单的电路的例子。电路的不同部分用标准电路符号表示。一个仪表测量电流通过电路的流量,一个电压计测量电压。一个阻力器是将某些电能转换为其他形式的电能的任何装置。例如,一个阻力器可能是灯泡或门铃。The circuit diagram on the right represents the circuit drawing on the left. Below are some of the standard symbols used in circuit diagrams.
::右侧的电路图代表左侧的电路图。下面是电路图中使用的一些标准符号。
Summary
::摘要-
An electric circuit is a closed loop through which current can flow.
::电路是一个闭路环,水流可以畅通无阻。 -
All electric circuits must have a voltage source, such as a battery, and a conductor, which is usually wire. They may have one or more electric devices as well.
::所有电路都必须有电压源,如电池和导电器,通常都是电线,还可能有一个或多个电动装置。 -
An electric circuit can be represented by a circuit diagram, which uses standard symbols to represent the parts of the circuit.
::电路可以用电路图表示,电路图使用标准符号表示电路的各个部分。
Review
::回顾1. What is an electric circuit?
::1. 什么是电路?2. Which two parts must all electric circuits contain?
::2. 所有电路必须包含哪些两部分?3. Why does the light bulb need to be connected to both battery terminals?
::3. 为什么灯泡需要连接到两个电池终端?4. Sketch a simple circuit that includes a battery, switch, and light bulb. Then make a circuit diagram to represent your circuit, using standard circuit symbols.
::4. 绘制一个包括电池、开关和灯泡的简单电路,然后用标准电路符号绘制一个电路图,代表你的电路。Circuit Diagrams - Example 1
::电路图图 - 示例1Distinguishing between open and closed circuits and determining whether or not electricity will flow.
::区分开路和闭路,确定电流是否正常。Watch the video at:
::观看影片在:Electrical Energy - Example 1
::电气能源 -- -- 例1Understanding Circuits
::理解电路Watch the video at:
::观看影片在:
Real World Example - Jacob's Ladder
::真实世界示例 - Jacob 的梯子
A functioning Jacob's ladder
::雅各的阶梯What happens when a circuit is almost complete? If a little piece of the circuit is missing, let's say an inch of wire, then the electricity will not flow through the circuit at all. Although this is accepted as true, it is not always the case. Occasionally, electrical arcs can “jump” small distances. In these situations, the electricity is flowing through the air. The reason for this is that air can conduct electricity (although it does have a very high resistance to it). The result is an air bridge that completes the circuit.
::当电路几乎完成时会发生什么情况?如果电路少了一小块电线,那么电就不会通过电路。 虽然这被接受为是真实的, 但情况并非总是如此。 有时电弧可以“跳动”小距离。 在这种情况下,电路通过空气流动。 原因是空气可以进行电路( 尽管对电路的阻力很大 ) 。 结果是一座通电的空桥。WARNING: The following device is extremely dangerous. High voltage electricity can cause extreme pain and harm to people. Please do not try to make one at home.
::警告:以下装置极其危险。高压电能会对人们造成极大痛苦和伤害。请不要试图在家里制造。There is a device designed to illustrate arc jumping called the Jacob's ladder. It utilizes two usually copper metal rods that go upwards and tilt away from each other. There is a problem that comes up when using such a device. No wall outlet offers enough voltage to allow the current to arc. Remember, V=IR. A transformer is used to increase the voltage in the circuit using induction. The output current has a much higher voltage that travels much more slowly. This voltage amperage combination is perfect for dealing with obstacles with high resistance such as the air and therefore essential to making arcing possible. Watch this video to see the Jacob's ladder in action:
::用于说明电弧跳跃的装置叫雅各布的梯子。 它通常使用两根铜金属棒, 它们向上倾斜。 当使用这样的装置时会出现问题。 没有墙出口能提供足够电压, 使电流向弧。 记住, V=IR。 一个变压器用感应来增加电路的电压。 输出电流的电压速度要慢得多。 这种电压振动组合非常适合处理高阻力障碍, 如空气, 因而对电弧至关重要 。 观看这个视频可以看到雅各布的梯子 :In watching the video, you probably noticed the electric arcs rise, eventually get to the top of the rods, disperse, then start again on the bottom. Why is that? When the arc is established, it creates a channel of super-heated gas in the air. Due to its higher temperature and therefore lower density, this gas rises causing the electric arc to move with it. When the arc reaches to the top of the rods or to a point where the distance between the rods prevents the electricity from arcing, that arc of the electricity ceases to exist. The arc then restarts along the path of least resistance, (where there is the least air between the rods) at the bottom of the rods restarting the process.
::在观看视频时,你可能注意到电弧上升,最终到达杆的顶部,散开,然后在底部重新开始。为什么?当弧建立起来时,它会在空气中创建一个超热气体通道。由于温度较高,因此密度较低,这种气体上升导致电弧随其而移动。当电弧到达杆的顶部,或者到达杆之间的距离阻止电弧升起的地方,电弧的弧就不再存在了。电弧再沿着阻力最小的路径重新开动,(在杆之间的空气最少)在杆的底部重新开始。Creative Applications:
::创意应用:1. What does the solder (easily meltable metal) do to the arcing current in the second half of the video? Why does this occur?
::1. 焊接器(易熔金属)对录像后半段的电流有何影响?为什么会发生这种情况?2. What factors determine how high an arc rises before it dissipates?
::2. 哪些因素决定弧消失前的升幅有多高?3. What are other examples of electrical arcing?
::3. 电弧的其他例子是什么? -
The voltage source of this simple circuit is a battery. In a home circuit, the source of voltage is an electric power plant, which may supply electric current to many homes and businesses in a community or even to many communities.
