问题
问答题 简答题
什么是交流电的周期.频率和角频率？
答案
参考答案：
交流电每重复一次所需的时间称为周期，用字母T表示，单位是秒（s）。交流电在1s内重复的次数，称为频率，用字母f表示，单位是赫兹（Ｈz）。角频率是指交流电在1s内变化的电角度，用字母ω表示，单位是弧度／秒（rad/s）。
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什么是交流电的周期.频率和角频率？
参考答案：
交流电每重复一次所需的时间称为周期，用字母T表示，单位是秒（s）。交流电在1s内重复的次数，称为频率，用字母f表示，单位是赫兹（Ｈz）。角频率是指交流电在1s内变化的电角度，用字母ω表示，单位是弧度／秒（rad/s）。
The weekend comes again. Grace is with her mother. She wants her mother to a new coat for her. In a clothes shop, she finds an orange coat. That’s her favourite colour. She tries it on, but it is too . She wants a larger (较大的) one. But the larger one is not . Grace doesn’t like other colours. Her mother says, “ go to another shop to have a look.” Then they go out of the shop and come into the next one. This shop is very big and there many kinds of coats. Grace likes an orange one and asks, “ is it?” “538 yuan,” answers the shop assistant (店员). Grace’s mother it is too expensive and she doesn’t have so money with her. “Would you like this orange one? It’s only 210 yuan,” says the shop assistant. “Oh, it looks good. Do you think so, Grace?” “OK. Let’s it.” Grace’s mother pays for it.
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