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什么是电流互感器？电流互感器的作用是什么？

答案

参考答案：

把大电流按规定比例转换为小电流的电气设备，称为电流互感器，用TA表示。TA有两个或者多个相互绝缘的线圈，套在一个闭合的铁芯上。原线圈匝数较少，副线圈匝数较多。TA的作用是把大电流按一定比例变为小电流，提供给各种仪表、继电保护及自动装置用，并将二次系统与高电压隔离。它不仅保证了人身和设备的安全，也使仪表和继电器的制造简单化、标准化，提高了经济效益

单项选择题

关于EDI，以______下是错误的。

A．EDI是两个或多个计算机应用系统之间的通信

B．EDI要求计算机之间传输的信息遵循—定的语法规则

C．EDI强调数据自动投递和处理而不需要人工的介入

D．EDI建立在开放的因特网平台之上
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单项选择题

(二)


"Sesame Street" has been called "the longest street in the world". That is because the television program by that name can now be seen in: so many parts of the world. That program became one of American’s exports soon after it went on the air in New York in 1969.
In the United States more than six million children watch the program regularly. The viewers include more than half the nation’s preschool children, from every kind of economic, racial, and geographical group.
Although some educators object to certain elements in the program, parents praise it highly. Many teachers also consider it a great help, though some teachers find that problems arise when first graders who have learned from "Sesame Street" are in the same class with children who have not watched the program.
Tests have shown that children from all racial, geographical, and economic backgrounds have benefited from watching it. Those who watch it five times a week learn more than occasional viewers. In the US the program is shown at different hours during the week in order to increase the number of children who can watch it regularly.
The programs all use songs, stories, jokes, and pictures to give children a basic understanding of numbers, letters and human relationships. But there are some differences. For example, the Spanish program, produced in Mexico City, devotes more time to teaching whole words than to teaching separate letters.
Why has "Sesame Street" been so much more successful than other children’s shows Many reasons have been suggested. People mention the educational theories of its creators, the support by the government and private businesses, and the skillful use of a variety of TV tricks. Perhaps an equally important reason is that mothers watch it along with their children. This is partly because famous adult stars often appear on it. But the best reason for: the success of the program may be that it makes every child watching feel able to learn. The child finds himself learning, and he wants to learn more.

Children who often watch the program ______ .

A．can have problems in school

B．will find it a great help

C．will take no interest in their studies

D．will be well educated
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