问题 实验题

我们可以通过以下实验,来探究产生感应电流的条件

⑴给岀的实物图中,请用笔画线代替导线补全实验电路;

⑵接好电路,合上开关瞬间,电流表指针       (填“偏转”或“不偏转”);

⑶电路稳定后,电流表指针           (填“偏转”或“不偏转”);

⑷根据以上实验可得:产生感应电流的条件                    

答案

⑴电路如图(2分) (2)偏转   (1分)(3)不偏转  (1分)(4)闭合回路磁通量发生变化(1分)

题目分析:(1)根据探究产生感应电流的条件,将螺线管B和电流表构成一个闭合回路,将螺线管A、电源、滑动变阻器构成一个闭合回路,如图所示;(2)合上开关瞬间,通过A螺线管的电流增大,则通过螺线管B的磁通量增大,根据感应电流产生的条件判定:有感应电流产生,电流表的指针偏转;(3)电路稳定后,通过A螺线管的电流不变,则通过螺线管B的磁通量不变,根据感应电流产生的条件判定:无感应电流产生,电流表的指针不偏转;(4)感应电流产生的条件为:只要闭合回路磁通量发生变化,就有感应电流产生。

单项选择题
单项选择题

Although there are many skillful Braille readers, thousands of other blind people find it difficult to learn that system. They are thereby shut (1) from the world of books and newspapers, having to (2) on friends to read aloud to them.

A young scientist named Raymond Kurzweil has now designed a computer which is a major (3) in providing aid to the (4) .His machine, Cyclops, has a camera that (5) any page, interprets the print into sounds, and then delivers them orally in a robot-like (6) through a speaker. By pressing the appropriate buttons (7) Cyclops’s keyboard, a blind person can "read" any (8) document in the English language.

This remarkable invention represents a tremendous (9) forward in the education of the handicapped. At present, Cyclops costs $ 50,000. (10) , Mr. Kurzweil and his associates are preparing a smaller (11) improved version that will sell (12) less than half that price. Within a few years, Kurzweil (13) the price range will be low enough for every school and library to (14) one. Michael Hingson, Director of the National Federation for the Blind, hopes that (15) will be able to buy home (16) of Cyclops for the price of a good television set.

Mr. Hingson’s organization purchased five machines and is now testing them in Maryland, Colorado, Iowa, California, and New York. Blind people have been (17) in those tests, making lots of (18) suggestions to the engineers who helped to produce Cyclops.

"This is the first time that blind people have ever done individual studies (19) a product was put on the market," Hingson said. "Most manufacturers believed that having the blind help the blind was like telling disabled people to teach other disabled people. In that (20) , the manufacturers have been the blind ones.

16()

A.models

B.modes

C.cases

D.collections