alter

alter: change, or make sb/sth change, from Latin alter 'other', alter ego: sb very like oneself
altar: 圣餐桌, 祭坛
alternate: occur in turn, or arrange by turns; 还可做形容词或名词
相关词形: alterable, alteration, alternating, alternation, alternator, alternative, alternatively

Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction.

Over 900 feet tall, the Baihetan dam has 16 units that can each generate 1 million kilowatts of energy. This energy-generating capacity makes it the second-largest in the world. The Baihetan Hydropower Station will produce more than 15 times the energy produced from the Hoover Dam, reports Global Times.

"We use an ultra-high voltage transmission system to transmit power from the western part of our country to the eastern part where clean energy sources are relatively scarce. The practice plays an big role in reducing carbon emissions in the industrially developed eastern regions," said He Wei, secretary of the Party Committee of the Construction Department of Baihetan Hydropower Station.

它是超巨型混流式水轮发电机组，每台重达8000多吨，比埃菲尔铁塔重1000多吨。它的高度超过50米，相当于18层楼。它是目前全球水力发电机的巅峰之作。

A schematic representation of long distance electric power transmission. From left to right: G=generator, U=step up transformer, V=voltage at beginning of transmission line, Pt=power entering transmission line, I=current in wires, R=total resistance in wires, Pw=power lost in transmission line, Pe=power reaching the end of the transmission line, D=step down transformer , C=consumers. 10000W有10000V*1A和100V*100A等多种组合。I越小Pw越小。

 

An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.

In electrical engineering, an armature is the component of an electric machine which carries alternating current. The armature windings conduct AC even on DC machines, due to the commutator action (which periodically reverses current direction) or due to electronic commutation, as in brushless DC motors. The word armature was first used in its electrical sense, i.e. keeper of a magnet, in mid 19th century.

In most generators, the field magnet is rotating, and is part of the rotor, while the armature is stationary, and is part of the stator. Both motors and generators can be built either with a stationary armature and a rotating field or a rotating armature and a stationary field.

Alternators are used in modern automobiles to charge the battery and to power the electrical system when its engine is running.

六级/考研单词: ego, oneself, alternate, reverse, magnitude, dam, million, globe, volt, transmit, scarce, carbon, emit, construct, consume, convert, rotate, component, conduct, electron, commute, motor, magnet, automobile