Section outline

  • Cables are attached to a car battery for a jump start from a live battery.

    Emily’s dad is giving his car battery a “jump” because the battery “died” overnight. He’s attaching cables to the terminals of the car battery. Then he will connect the other ends of the cables to the terminals of a “live” battery. The cables will carry electric current to the dead battery, providing the needed for the car to start.
    ::Emily的爸爸正在给他的汽车电池一个“跳跃 ” , 因为电池“死 ” 过夜。 他把电缆挂在汽车电池的终端上。 然后他将把电缆的另外两端连接到“活”电池的终端上。 电缆将把电流输送到死电池上,提供汽车启动所需的设备。

    Flowing Charges
    ::流动支出

    Electric current is a continuous flow of electric charges (electrons). Current is measured as the amount of charge that flows past a given point in a certain amount of time. The SI unit for electric current is the ampere (A), or amp. Electric current may flow in just one direction (direct current), or it may keep reversing direction (alternating current). 
    ::电流是电电流( 电子电流) 。 电流是电流的连续流。 电流是用特定时间流过某一点的电量来衡量的。 电流的光量是安培( A) , 即电流。 电流可能仅流向一个方向( 直接流 ) , 或它可能不断逆向( 交替流 ) 。

    Q: Why do you think charges flow in an electric current?
    ::问:你为什么认为电流会充电?

    A: Electric charges flow when they have electric . Potential energy is stored energy that an object has due to its position or shape.
    ::A:电荷在有电时会流动。潜在的能量是一个物体因其位置或形状而储存的能量。

    Electric Potential Energy
    ::电力潜能能源

    Electric potential energy comes from the position of a charged particle in an electric field . For example, when two negative charges are close together, they have potential energy because they repel each other and have the potential to push apart. If the charges actually move apart, their potential energy decreases. Electric charges always move spontaneously from a position where they have higher potential energy to a position where they have lower potential energy. This is like water falling over a dam from an area of higher to lower potential energy due to gravity.
    ::电的潜在能量来自电场中充电粒子的位置。 例如,当两个负电荷相近时,它们具有潜在的能量,因为它们互相反射,并有可能分裂。 如果电荷实际分开,它们的潜在能量就会减少。电荷总是会自发地从具有较高潜在能量的位置转移到具有较低潜在能量的位置。这就像水从一个较高地区从一个大坝掉到由于重力而潜在能量更低的地区。

    Voltage
    ::电压

    For an electric charge to move from one position to another, there must be a difference in electric potential energy between the two positions. A difference in electric potential energy is called voltage . The SI unit for voltage is the volt (V). Look at the Figure . It shows a simple . The source of voltage in the circuit is a 1.5-volt battery. The difference of 1.5 volts between the two battery terminals results in a spontaneous flow of charges, or electric current, between them. Notice that the electrons flow from the negative terminal to the positive terminal because electrons are negatively charged and are repelled by the negative terminal.
    ::电荷要从一个位置移动到另一个位置,两个位置之间在电潜能能源方面必须存在差异。电潜能能量的差别称为电压。电潜能能量的差别是电压的差别。SI电压单位是电压(V)。看看图。它显示了一个简单。电路电压来源是1.5伏电池。两个电池终端之间的1.5伏差导致电荷自发流动,或电流。注意电子从负终端流到正终端,因为电荷受到负电荷,并被负终端击退。

    Simple circuit diagram showing a 1.5-volt battery as voltage source with connections.

    Q: You might put a 1.5-volt battery in a TV remote. The battery in a car is a 12-volt battery. How do you think the current of a 12-volt battery compares to the current of a 1.5-volt battery?
    ::问题:您可以在电视遥控器中安装1.5伏电池。汽车中的电池是12伏电池。您认为12伏电池的电流与1.5伏电池的电流相比如何?

    A: Greater voltage means a greater difference in potential energy, so the 12-volt battery can produce more current than the 1.5-volt battery.
    ::A: 更大的电压意味着潜在能量的差别更大,因此12伏电池的电流比1.5伏电池的电流要大。

     

     

    Summary
    ::摘要

    • Electric current is a continuous flow of electric charges. The SI unit for electric current is the ampere (A).
      ::电流是电流源源源不断的电流,SI电流装置是安培(A)。
    • An electric charge flows when it has electric potential energy due to its position in an electric field. An electric charge always moves spontaneously from a position of higher to lower potential energy.
      ::当电荷因其在电场的位置而具有潜在的电能时,电费就会流动。 电费总是会自发地从高到低的电能。
    • For an electric charge to move from one position to another, there must be a difference in electric potential energy between the two positions. This difference is called voltage. The SI unit for voltage is the volt (V).
      ::电费要从一个位置移动到另一个位置,两个位置之间在电力潜力方面必须存在差异,这种差异称为电压。

    Review
    ::回顾

    1. What is electric current? Name the SI unit for electric current.
      ::什么是电流? 命名电流的SI单位 。
    2. Explain what gives a charge electric potential energy. Describe an example.
      ::解释什么能给电源充电 举个例子
    3. How is electric potential energy related to the direction an electric charge spontaneously moves?
      ::电能如何与电荷自发移动的方向相关?
    4. What is voltage, and why is it needed for charges to flow in an electric current?
      ::什么是电压? 为什么电流需要电压?