机电专业英语L21.ppt

Lesson 21 Voltage 电压;As you have seen, there is a force of attraction between a positive and a negative charge. A certain amount of energy must be exerted in the form of work to overcome the force and move the charges a given distance apart. All opposite charges possess a certain potential energy because of the separation between them. The difference in potential energy of the charges is the potential difference.;As you have seen, there is a force of attraction between a positive and a negative charge.正如你所知的，正电荷和负电荷之间存在吸引力。A certain amount of energy must be exerted in the form of work to overcome the force and move the charges a given distance apart.克服吸引力将电荷移动一定距离，需要以做功形式消耗一定能量。All opposite charges possess a certain potential energy because of the separation between them.由于正负电荷之间的距离，所有异性电荷都具有一定的势能。The difference in potential energy of the charges is the potential difference.电荷之间的势能差就是电势差。;Electric field of a positive and a negative point charge.;For example, consider a water tank that is supported several feet above the ground. A given amount of energy must be exerted in the form of work to pump water up to fill the tank. Once the water is stored in the tank, it has a certain potential energy which, if released, can be used to perform work. For example, the water can be allowed to fall down a chute to turn a water wheel.;For example, consider a water tank that is supported several feet above the ground.举例，想象一个水箱被支撑在地面以上几英尺。A given amount of energy must be exerted in the form of work to pump water up to fill the tank.抽水来填满水箱，需要以做功的形式消耗一定能量。Once the water is stored in the tank, it has a certain potential energy which, if released, can be used to perform work.一旦水被装在水箱中，它就具有一定的势能，如果释放，可用被用来做功。For example, the water can be allowed to fall down a chute to turn a water wheel.比如，水可以倾泄下来成为水流来转动水轮。;Potential difference in electrical terms is more commonly called voltage (V) and is expressed as energy or work (W) per unit charge (Q) : V= W/Q Where W is expressed in joules (J)