104 Setting Up Circuits-High

Setting Up Circuits FOCUS Question How does electricity flow through a circuit?

设置电路焦点问题电流是如何流过电路的?

Electrifying! You walk into a room, flip a switch and, like magic, the room instantly lights up. But it's not magic. It's electricity and the science of atoms. An atom is the smallest part of an element that can exist by itself. Atoms have three parts— neutrons, protons, and electrons. Neutrons and protons make up the nucleus, or center, of the atom. The negatively charged electrons inside the atom swirl around the nucleus, forming rings. The electrons in the outermost ring can jump from one atom to the next, and when they do, an electric current flows. An electric current is the electricity that runs through power lines, the wires in your house, and even a flashlight.

令人振奋的!你走进一个房间，按下开关，房间就像变魔术一样立刻亮了起来。 但这不是魔法。这是电和原子科学。 原子是元素中可以独立存在的最小部分。 原子有三部分——中子、质子和电子。 中子和质子组成原子核，即原子的中心。 原子内部带负电的电子绕着原子核旋转，形成环。 最外层环上的电子可以从一个原子跳到下一个原子，当它们这样做时，就会产生电流。 电流是通过电力线、房子里的电线，甚至是手电筒的电流。

Powering the Circuit To get from one place to another, an electric current travels through a closed, looped pathway called a circuit. Every circuit starts with a power source to get electrons moving. Many sources can power a circuit, including power plants, batteries, windmills, and solar cells. Electric current runs through a circuit in one of two ways. The simplest is direct current (DC), in which electrons move around the circuit in just one direction. Batteries are a source of direct current, which is good for powering simple toys and gadgets. More complex circuits require alternating current (AC). Instead of racing one way around a circuit like cars around a racetrack, the speedy electrons in an alternating current keep reversing direction. (Don't try this on a real racetrack!)

电流从一个地方到另一个地方，要通过一个封闭的环形路径，称为电路。 每个电路都有一个电源来让电子运动。 许多来源可以为电路供电，包括发电厂、电池、风车和太阳能电池。 电流通过电路有两种方式。 最简单的是直流电(DC)，电子在电路中只沿一个方向移动。 电池是直流电的来源，可以很好地为简单的玩具和小玩意供电。 更复杂的电路需要交流电(AC)。 这些高速的电子在交流电中不断地反向运动，而不是像汽车在赛道上那样在电路中单向运动。 (不要在真正的赛道上尝试这个!)

Go with the Flow In both DC and AC currents, a power source gets the electrons moving, but it's a conductor that moves the electric current along the circuit. Metal wires made of copper, aluminum, or silver make good conductors. In the atoms of these metals, electrons are loosely bound to the outer ring and can easily move to new atoms and create a current. In fact, the electrons move so much that insulators are needed to keep the current from exiting the wires. In insulators, such as rubber or plastic, the atoms have tightly-bound electrons that block the flow of electricity. Next, the circuit transfers electricity to a device, or a load, that uses the energy. Washing machines, computers, and lightbulbs are loads that use the energy in a circuit. Loads convert electrical energy into other forms of energy. Lightbulbs, for example, change electricity into light and heat. Radios are loads that convert electrical energy into sound energy.

在直流和交流电流中，电源都能使电子移动，但它是一种导体，使电流沿着电路移动。 由铜、铝或银制成的金属线是良导体。 在这些金属的原子中，电子被松散地束缚在外环上，很容易移动到新的原子上并产生电流。 事实上，电子移动得如此之快，以至于需要绝缘体来防止电流从电线中流出。 在绝缘体中，如橡胶或塑料，原子有紧密结合的电子，可以阻止电流的流动。 接下来，电路将电流传输到使用能量的设备或负载上。 洗衣机、电脑和灯泡都是使用电路中的能量的负载。 负载将电能转换成其他形式的能量。 例如，灯泡将电转化为光和热。 收音机是把电能转换成声能的负载。

Components of Circuits A simple circuit is made up of a power source, a conductor, and a load. More complex circuits have additional parts. 1 Capacitors temporarily store a charge. In some circuits, they block direct current while allowing alternating current to pass by. They help stabilize power flow in circuits. 2 A resistor is a part of a circuit that reduces the flow of current. Resistors keep loads from becoming too hot and allow people to control the amount of current flowing through a circuit. 3 A transistor is a device that is used as a switch to open or close the circuit or to amplify (strengthen) the electrical signal in a circuit.

电路的组成一个简单的电路由电源、导体和负载组成。 更复杂的电路有额外的部件。 电容器暂时储存电荷。 在一些电路中，它们阻挡直流电而允许交流电通过。 它们有助于稳定电路中的电流。 电阻器是电路中减小电流的一部分。 电阻器可以防止负载变得太热，并允许人们控制流经电路的电流。 晶体管是一种用来打开或关闭电路或放大(加强)电路中的电信号的开关。

Circuit parts such as transistors, resistors, and capacitors have a number of real-world functions. Transistors are often used in mobile phones, televisions, and hearing aids. They help make sounds louder and transmit radio waves. Transistors inside machines called pacemakers help regulate the heartbeat of patients with abnormal heart rhythms. Resistors help avoid an interruption to the current, called a short circuit. They control the volume in TVs and radios. Resistors even allow us to light our houses the way we want by regulating dimmer switches on lights that have multiple settings. Capacitors help radios tune into a specific frequency. They also keep machines like alarm clocks working even if the rest of the power to a household is interrupted. Do You Know? Cameras use capacitors to create a flash.

电路部件，如晶体管、电阻器和电容器，具有许多实际功能。 晶体管常用于移动电话、电视和助听器。 它们有助于使声音更大，并传输无线电波。 被称为心脏起搏器的机器内部的晶体管有助于调节心律异常患者的心跳。 电阻器有助于避免电流中断，即短路。 他们控制电视和收音机的音量。 电阻甚至可以让我们通过调节有多种设置的灯的调光开关，以我们想要的方式照亮我们的房子。 电容器帮助收音机调谐到特定的频率。 即使家庭的其他电力中断，它们也能使闹钟等机器正常工作。 你知道吗?照相机使用电容器来产生闪光。