章节大纲

  • Row of electric generators in a hydroelectric power station with overhead structure.

    These large machines are electric generators. This particular row of generators is installed in a hydroelectric power station. The insides of these generators are coils of wire spinning in a . The relative motion between the wire and the magnetic field is what generates electric current . In all generators, some mechanical energy is used to spin the coil of wire in the generator. In the case of hydroelectric power, the coil of wire is spun by water falling from higher  @$\begin{align*}PE\end{align*}@$ to lower @$\begin{align*}PE\end{align*}@$ . Windmills and steam turbines are used in other types of power generators to spin the coil.
    ::这些大型机器是发电机。 这几排发电机安装在一个水电站。 这些发电机的内脏是电线旋转的圈子。 电线和磁场之间的相对运动是产生电流的产物。 在所有发电机中, 一些机械能源被用来旋转发电机中的电线圈。 在水电方面, 电线圈被从高点@ $\ begin{ aliign\\ end\ leign\ legn{ align\ $ 降点@ $\ begin{ align} PE\ end{ align} $ 。 风车和蒸汽涡轮机被用于其他类型的电源发电机来旋转电线圈。

    Electric Generators

    ::发电机

    Electric generators convert mechanical energy to electric . The generator consists of some number of wire loops wrapped around an iron core and placed in a strong magnetic field. The loops of wire and the iron core are called the armature . The armature is mounted so that it can rotate freely inside the magnetic field. Mechanical energy is used to spin the armature in the field so that the wire loops cut across the field and produce electric current. The  @$\begin{align*}EMF\end{align*}@$ of this current is calculated by @$\begin{align*}EMF = Blv\end{align*}@$ .
    ::电源发电机将机械能源转换为电能。 发电机由一些环绕铁芯并放置在强大磁场的铁芯铁环组成。 铁环和铁芯的环被称为臂状。 将臂状安装, 以便在磁场内自由旋转。 机械能被用来在田间旋转臂状, 使铁环横穿田间, 产生电流 。 此电流中的电环由 @$\ begin{ ALign} EMF = Blv\ end{ ALign} 计算 。 @ $\ begin{ leign\ EMF = Blv\ end{align} 计算 $ 。 @ $\ begin{ = Blv\ end} allign}

    Sketch illustrating an electric generator with wire loops in a magnetic field, showcasing current flow concepts.

    Consider the coil and magnetic field sketched above. When the right hand side of the coil moves up through the field, the left hand rule indicates that the electron flow will be from the front to the back in that side of the coil. The current generated will have the greatest  @$\begin{align*}EMF\end{align*}@$ as the wire is cutting perpendicularly across the field. When the wire reaches the top of its arc, it is moving parallel to the field and therefore, not cutting across the field at all.  The  @$\begin{align*}EMF\end{align*}@$ at this point will be zero. As that same wire then cuts down through the field as it continues to spin, the left hand rule indicates that the electron flow will be from the back to the front in that side of the coil. In this second half of the arc, the direction of the electron flow has reversed. The magnitude of the  @$\begin{align*}EMF\end{align*}@$ will reach maximum again as the wire cuts perpendicularly down through the field and the  @$\begin{align*}EMF\end{align*}@$ will become zero again as the wire passes through the bottom of the arc. The current produced as the armature goes around will resemble a sine wave where the  @$\begin{align*}EMF\end{align*}@$ reaches a maximum in one direction, then goes to zero, then goes to a maximum in the other direction. This type of current is called alternating current . By having more and more loops of wire on the armature, the crests and troughs overlap and fill in until a constant current is produced.
    ::考虑上面的线条和磁场。 当线条右手侧通过字段向上移动时, 左手规则显示, 电子流将从前向后, 在尾线的右侧。 当电线横跨字段时, 产生的电流将最大@ $\ begin{ ALign\\ EMF\ end{ ALign} 。 当电线直切到电弧的顶端时, 它会与字段平行移动, 因此, 它不会横跨字段。 @ $\ begin{ align} EMF=end{ end{ 最高值} 。 当电线在继续旋转时, 当电流从右向下时, 电流将再次从右向下, 电流将再次从右转至右流 。 直流的直线将随着正弦的直流向下方的直流向下方方向 。 直线将再次向右转至右方的直向下方 。

    Graph showing a sine wave with crests and troughs, representing alternating current.

    A direct current is one that always flows in the same direction rather than alternating back and forth. Batteries produce direct currents. A generator can also produce direct current by using a split ring commutator that changes external connections every half turn of the armature so that even though the current in the coil changes direction, every time the current in the coil changes direction, the external connection switches so that the external current always goes in the same direction.
    ::直接电流总是向同一方向流动,而不是往返。电池产生直接电流。发电机也可以通过使用一个分环交换器来产生直接电流,该交换器每半个臂形转弯改变外部连接,这样,即使循环中的电流改变方向,每当循环中的电流改变方向时,外部连接开关就会使外部电流向同一方向移动。

    Generators and motors are almost identical in construction but convert energy in opposite directions. Generators convert mechanical energy to electrical energy and motors convert electrical energy to mechanical.
    ::发电机和发动机在建筑业几乎完全相同,但能向相反方向转换,发电机将机械能源转换为电力能源,发动机将电力能源转换为机械能源。

    Because of the alternating direction in alternating current, the average value is less than the power supplied by a direct current. In fact, the average power of an AC current is one-half its maximum power and one-half the power of an equivalent DC current. The effective current of an AC generator is 0.707 times its maximum current. The same is true for the effective of an AC generator.
    ::由于交替交替的电流方向交替,平均值低于直接电流提供的力量。 事实上, AC 电流的平均功率是其最大功率的一半, 相当于 DC 电流的一半。 AC 发电机的有效功率是其最大电流的0. 707倍。 AC 发电机的有效功率也是如此。

    @$\begin{align*}I_{\text{eff}} = 0.707 \ I_{\text{max}} \end{align*}@$
    ::@ $\ begin{ align} I\\\ text{ ffeff} = 0. 707 \ I\ text{ max}\ end{ ALign} $ @ $

    @$\begin{align*}V_{\text{eff}} = 0.707 \ V_{\text{max}}\end{align*}@$
    ::@ $\ begin{ align} Vtext{ ffeff} = 0. 707 \ Vtext{ max} end{ ALign} $

    Example  
    ::示例示例示例示例

    An AC generator develops a maximum voltage of 34.0 V and delivers a maximum current of 0.170 A.
    ::空调发电机开发最大电压为34.0V,输出最大电流为0.170 A。

    1. What is the effective voltage of the generator?
      ::发电机的有效电压是多少?
    2. What is the effective current delivered by the generator?
      ::发电机有效输送的电流是什么?
    3. What is the in the ?
      ::这里面是什么?

    Answers
    ::答复答复答复

    1. @$\begin{align*}V_{\text{eff}} = 0.707 \ \ V_{\text{max}} = (0.707)(34.0 \ V) = 24.0 \ V\end{align*}@$
      ::@ $\ begin{ legin} {V\\\ text} {ffeff} = 0. 707\\ V\ text{ max} = ( 0. 707) (34. 0\ V) = 24.0\ V\ end{ end{ align$} = ( 0. 707\ V\ text{ max} = ( 0. 707) (34. 0\ V) = 24.0\ V\end{ end{ leg $ * </span> </li> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> <span class="x-ck12-mathEditor" data-contenteditable="false" data-edithtml="" data-math-class="x-ck12-math" data-mathmethod="inline" data-tex="I_%7B%5Ctext%7Beff%7D%7D%20%20%3D%200.707%20%5C%20%5C%20I_%7B%5Ctext%7Bmax%7D%7D%20%3D%20(0.707)(0.17%20%5C%20A)%20%3D%200.120%20%5C%20A"> @$\begin{align*}I_{\text{eff}} = 0.707 \ \ I_{\text{max}} = (0.707)(0.17 \ A) = 0.120 \ A\end{align*}@$
      ::@ $\ begin{ legign} I\\\ text{ ffeff} = 0. 707\ \ I\ text{ max} = ( 0. 707) (0. 17\ A) = 0. 120\ A\ end{ align$ = </span> </li> <button class="play-button btn btn-success" style="float: right;" value="@s"> 播放段落 </button> <li> <span class="x-ck12-mathEditor" data-contenteditable="false" data-edithtml="" data-math-class="x-ck12-math" data-mathmethod="inline" data-tex="R%3D%5Cfrac%7BV%7D%7BI%7D%3D%5Cfrac%7B24.0%20%5C%20V%7D%7B0.120%20%5C%20A%7D%3D200.%20%5C%20%5COmega"> @$\begin{align*}R=\frac{V}{I}=\frac{24.0 \ V}{0.120 \ A}=200. \ \Omega\end{align*}@$
      ::@ $\ begin{ legin{ legin}Rfrac{ VIfrac{ 24.0\ V0. 120\ A200.\\ \ omega\ end{ legn{ legn} \ legn{ legn} @ $\ begin{ legin} $\ begin{ legin{ r\ rac{ VI}\ frac{ 24.0\ V0. 120\ A200.\\\\ \ \ omega\ end{ leg{ leg}

    Summary
    ::摘要

    • Electric generators convert mechanical energy to electric energy.
      ::发电机将机械能源转换为电力能源。
    • The generator consists of some number of wire loops wrapped around an iron core and placed in a strong magnetic field.
      ::产生器由一些铁芯环绕的铁芯环组成,并放置在一个强大的磁场。
    • The loops of wire and the iron core are called the armature.
      ::铁线和铁芯的循环被称为臂状。
    • The armature is mounted so that it can rotate freely inside the magnetic field.
      ::在磁场内自由旋转。
    • Mechanical energy is used to spin the armature in the field so that the wire loops cut across the field and produce electric current.
      ::机械能源被用来在田间旋转臂,以便铁丝环横穿田间,产生电流。
    • The current produced as the armature goes around will resemble a sine wave where the  @$\begin{align*}EMF\end{align*}@$ reaches a maximum in one direction, then goes to zero, then goes to a maximum in the other direction. This type of current is called alternating current.
      ::当臂形转动时生成的当前将类似于正弦波, 即@$\ begin{ align\ EMF\ end{ align} $ 在一个方向达到最大值, 然后转到零, 然后在另一个方向达到最大值。 此类型的当前值被称为交替当前值 。
    • A generator can also produce direct current by using a split ring commutator that changes external connections every half turn of the armature so that even though the current in the coil changes direction, every time the current in the coil changes direction, the external connection switches so that the external current always goes in the same direction.
      ::发电机还可以通过使用一个分环交换器来产生直接电流,该交换器每半个臂形转弯改变外部连接,这样,即使圆圈的电流改变方向,但每次在圆圈的电流改变方向时,外部连接开关就会使外部电流向同一方向移动。
    • The effective current of an AC generator is 0.707 times its maximum current.
      ::空调发电机的有效电流是最大电流的0.707倍。
    • The effective voltage of an AC generator is 0.707 times its maximum voltage.
      ::空调发电机的有效电压是最大电压的0.707倍。

    Review
    ::回顾

    1. What three things are necessary to produce  @$\begin{align*}EMF\end{align*}@$  mechanically?
      1. magnet, force lines, and magnetic field
        ::磁、力线和磁场
      2. @$\begin{align*}EMF\end{align*}@$ , conductor, and magnetic field
        ::@ $\ begin{ aliign\ EMF\ end{ end{ leign} $, 指挥器和磁场
      3. conducting wire, magnetic field, and relative motion
        ::电线、磁场和相对运动
      4. conducting wire, electrical field, and relative motion
        ::进行电线、电场和相对运动
      5. none of these will produce  @$\begin{align*}EMF\end{align*}@$ mechanically
        ::其中无一生产@$\ begin{ align\\ EMF\ end{ align\ $ 机械化$ </span> </li> </ol> <br/> <span style="color: green; "> ::要生产 @ $\ begin{ align\ EMF\ end{ align\ $ 机械化? 磁力、 武力线和磁场 @ $\ begin{ ALign} EMF\ end{ ALign}$、 指挥器和磁场进行电线、 磁场和相对运动进行电线、 电场和相对运动, 需要三样东西才能产生 ? 磁力、 武力线和磁场@ $\ begin{ ALign} 和磁场@ begin{ EMF\ end= ALign}$ 机械化不会产生@ $
      6. Increasing which of the following will increase the output of a generator?
        1. @$\begin{align*}EMF\end{align*}@$
          ::@$\ begin{ aliign\\ EMF\ end{ end{ leign} $ @ $
        2. strength of the magnetic field
          ::磁场强度
        3. resistance of the conductor
          ::控制导体的抗力
        4. load on the meter
          ::计时器上加载
        5. none of these
          ::没有任何这些

        ::@$\ begin{ align\\ EMF\ end{ end{ ALign}$$$ 显示器载荷在仪表上的磁场抗力
      7. The current in the rotating coil of all generators is
        1. AC
          ::AC( AC) AC
        2. DC
          ::DC DC
        3. pulsating AC
          ::脉动空调
        4. pulsating DC
          ::动脉冲 DC

        ::所有发电机旋转圈中的当前电流是 AC DC 脉动 AC 脉动 DC
      8. A generator in a power plant develops a maximum voltage of 170. V.
        1. What is the effective voltage?
          ::什么是有效的电压?
        2. A 60.0 W light bulb is placed across the generator. A maximum current of 0.70 A flows through the bulb. What effective current flows through the bulb?
          ::A 6 0. 0 W 灯泡放置在发电机上方。 最大流量为 0. 70 A 流经灯泡。 电流通过灯泡的有效流量是多少?
        3. What is the resistance of the light bulb when it is working?
          ::灯泡在起作用时的抵抗力是什么?

        ::发电厂的发电机能开发最大电压170. V. 有效电压是多少? 在发电机上方放置了60.0 W光灯灯泡。 最大电流为0. 70 A 流经灯泡。 在灯泡上流的电流是多少? 灯泡在起作用时的阻力是什么?
      9. The effective voltage of a particular AC household outlet is 117 V.
        1. What is the maximum voltage across a lamp connected to the outlet?
          ::与出口相连的灯具上的最大电压是多少?
        2. The effective current through the lamp is 5.50 A. What is the maximum current in the lamp?
          ::通过灯的电流是5.50A。 灯的最大电流是什么?

        ::特定AC家庭出口的有效电压是117 V。 连接到出口的灯具的最大电压是多少? 灯具的有效电流是5.50 A。 灯具的最大电流是多少?

      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. Which of the two generators in the video (an AC generator and a DC generator) involves a magnetic field?
        ::录像中的两个发电机(一个空调发电机和一个DC发电机)中哪一个涉及磁场?
      2. Which of the two generators in the video involves a wire-wrapped armature?
        ::视频中的两个发电机中哪一个 涉及一个有线包装的手臂?
      3. What is the difference between the DC generator and the AC generator?
        ::DC发电机和AC发电机有什么区别?