(6分)閱讀下面短文

會發(fā)光的電磁翹翹板

小明制作了如圖1 6(a)所示的電磁翹翹板參加學(xué)校的科技節(jié)活動.該電磁翹翹板是在兩端封閉的透明塑料管中放有一塊磁性很強(qiáng)的磁鐵,塑料管外繞有金屬絲作為線圈,在線圈兩端并聯(lián)兩只發(fā)光二極管(符號),其電路如圖l 6(b)所示.二極管具有單向?qū)щ娦,電流只能從二極管的正極流入,負(fù)極流出.演示時(shí),將塑料管上下翹動,磁鐵便在線圈中左右移動,相當(dāng)于線圈導(dǎo)體在磁場中做切割磁感線運(yùn)動,這時(shí)會看見兩只發(fā)光二極管輪流發(fā)光.

請回答下列問題:

(1)電磁翹翹板中發(fā)光二極管輪流發(fā)光是根據(jù)    原理工作的,    也是根據(jù)這一原理工作的(填“電動機(jī)”或“發(fā)電機(jī)").

(2)電磁翹翹板上下翹動時(shí),為什么發(fā)光二極管會輪流發(fā)光?

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科目:初中物理 來源: 題型:閱讀理解

完形填空 (共20小題;每小題1分,滿分20分)
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Certainly dustmen prefer to be known as "Reuse Collection and Disposal Officers". You may think that this is rather    36 , and it is better to call a spade a spade. But dustmen can be as    37  as people of any other occupation, though we must     38   that their job is not a    39    one in the world. We often take dustmen for granted. Perhaps because they usually come very early in the morning, before most people are     40   .We are likely to forget their     41   .Our dustbins are    42   regularly, but we    43    stop to think about the men who do this. However, it is one of the most important jobs in the world, and when there are no dustmen to    44   the rubbish, the general    45   soon becomes aware that something is wrong. Recently, the dustmen of England went on strike for higher wages.
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科目:初中物理 來源: 題型:閱讀理解

(6分)閱讀下面短文

內(nèi)   能

內(nèi)能是指物體內(nèi)部所包含的總能量,包括分子的動能(即分子無規(guī)則熱運(yùn)動動能)、分子的勢能(即分子間相互作用能)、分子內(nèi)的能量、原子內(nèi)的能量、原子核內(nèi)的能量等.在熱學(xué)中,由于在熱運(yùn)動中上述后三項(xiàng)能量不發(fā)生變化,所以內(nèi)能一般指前兩項(xiàng).由于分子的動能跟溫度有關(guān),分子的勢能跟分子間的距離有關(guān),所以物體的內(nèi)能跟溫度、體積都有關(guān)系.

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(1)慢慢壓縮針筒里的氣體,氣體內(nèi)能中哪部分發(fā)生變化?答:______________________________.

(2)加熱針筒里的氣體,氣體內(nèi)能中哪部分發(fā)生變化?答:__________________________________.

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科目:初中物理 來源: 題型:閱讀理解

(6分)閱讀下面短文

會發(fā)光的電磁翹翹板

小明制作了如圖1 6(a)所示的電磁翹翹板參加學(xué)校的科技節(jié)活動.該電磁翹翹板是在兩端封閉的透明塑料管中放有一塊磁性很強(qiáng)的磁鐵,塑料管外繞有金屬絲作為線圈,在線圈兩端并聯(lián)兩只發(fā)光二極管(符號),其電路如圖l 6(b)所示.二極管具有單向?qū)щ娦裕娏髦荒軓亩䴓O管的正極流入,負(fù)極流出.演示時(shí),將塑料管上下翹動,磁鐵便在線圈中左右移動,相當(dāng)于線圈導(dǎo)體在磁場中做切割磁感線運(yùn)動,這時(shí)會看見兩只發(fā)光二極管輪流發(fā)光.

  請回答下列問題:

(1)電磁翹翹板中發(fā)光二極管輪流發(fā)光是根據(jù)    原理工作的,    也是根據(jù)這一原理工作的(填“電動機(jī)”或“發(fā)電機(jī)").

 (2)電磁翹翹板上下翹動時(shí),為什么發(fā)光二極管會輪流發(fā)光?

查看答案和解析>>

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