#3 - The power of an engine 发动机的力量
1.Imagine having to walk or run everywhere, instead of riding in a car.
Engines are machines that use fuel to do work for us and make life easier. Fuel is a substance that has chemical energy stored inside it. The energy is released as heat by burning or exploding the fuel in the engine.
V This is an engine, there are many other kinds of engines. V
2.Most cars have petrol engines.
An air and petrol mixture is pushed into a hollow chamber called a cylinder. A spark from a Spark plug makes it explode, which pushes a piston down inside the cylinder. This movement is used by gears to turn the wheels. Most cars have four or six cylinders.
V This is a picture showing parts of the engine inside. V
3.A diesel engine doesn't use sparks.
The mixture of air and diesel is squashed in the cylinder, becoming so hot it explodes. Diesel engines are used in machines such as tractors that need lots of power.
V This is a Diesel engine model. V
4.A Jet engine mixes air and kerosene and sets fire to it in one long, continuous, roaring explosion.
Incredibly hot gases blast out of the back of the engine. These push the engine forward - along with the plane.
V This is a picture showing the parts in a jet engine. V
5.An electric motor passes electricity through coils of wire.
This makes the coils magnetic, and they push or pull against magnets around them. The push-pull makes the coils spin on their shaft (axle).
V This is a basic electric motor diagram. V
6.Engines that burn fuel give out gases and particles through their exhausts.
Some of these gases are harmful to the environment. The less we use engines, the better. Electric motors are quiet, efficient and reliable, but they still need fuel - to make the electricity at the power station.
想象不得不走到任何地方，而不是骑在车里。
发动机是使用燃料为我们做工作并使生活更轻松的机器。燃料是一种能够储存化学能的物质。能量通过燃烧或爆炸发动机中的燃料而被释放。
V这是一个引擎，还有很多其他种类的引擎。 V
大多数汽车都有汽油发动机。
将空气和汽油混合物推入称为圆筒的中空室中。火花塞的火花使其爆炸，将活塞推向气缸内。这种运动被齿轮用于转动车轮。大多数汽车有四六缸。
V这是显示内部发动机部件的图片。 V
柴油发动机不使用火花。
空气和柴油的混合物在气缸中挤压，变得如此热，它爆炸。柴油发动机用于需要大量动力的拖拉机等机器。
V这是柴油发动机型号。 V
喷气发动机混合空气和煤油，并在一个长时间连续的咆哮爆炸中燃烧。
令人难以置信的热气体从发动机的后面喷出。这些推动发动机向前 - 与飞机一起。
V这是显示喷气发动机部件的图片。 V
电动机通过电线通过电线。
这使得线圈成为磁性，并且它们推动或拉动围绕它们的磁体。推拉使线圈在其轴（轴）上旋转。
V这是一个基本的电动机图。 V
燃烧燃料的发动机通过排气排出气体和颗粒。
其中一些气体对环境有害。引擎越少越好。电动机是安静，高效和可靠的，但它们仍然需要燃料 - 在发电站做电。
