问题 实验题

小明学习了焦耳定律Q=I2Rt后,他想用如图所示的实验器材继续探究“电压一定时,电流的热效应与电阻的关系”,其中瓶内电阻丝的长度、粗细都相同。

(1)他将电路设计成并联的目的是                

(2)电流产生热量的多少不易直接测量。因此,在这个实验中是通过__________显示电流产生热量的多少的:这种用能直接观测的量来显示不易直接观测的量的方法叫“转换法”。这种方法在物理学的研究中经常用到,请你列举一例:__________________。

(3)两个瓶中用煤油而不用水的原因是                 

(4)在这个实验中,除了控制电压一定外,还要控制的量有__________。

(5)小明在实验中发现,在相同时间内甲瓶内的电阻丝放出的热量较多,根据你所学知识判断,甲乙两电阻的阻值较大的是:__________(甲/乙)。

答案

(1)电压相等          (2)温度计示数变化    略

(3)煤油的比热容小,温度计示数上升明显(水的比热容大,示数上升不明显)

(4)煤油的质量(相同的瓶子)

(5)乙

题目分析:(1)因为电阻并联时两端电压相等,所以两电阻并联,目的是保证电压相等;

(2)实验中通过温度计升高的示数来判断产生热量的多少;如:研究电磁铁磁性强弱的因素时,用电磁铁吸收小铁钉的数目多少来判断磁性的强弱;

(3)煤油的比热容小,在吸收热量相等的情况下,温度计示数上升明显,所以用煤油而不用水;

(4)此实验充分显示了控制变量法的应用.注意控制煤油的质量、通电时间和煤油的初温.

(5)根据公式得,在电压一定时,电阻越小,产生的热量越多.因为甲导线电阻小,乙电阻阻值大.

点评:此题主要通过实验考查了探究了“电压一定时,电流的热效应与电阻的关系”,考查了学生对实验的设计、控制变量法及转换法的应用.

填空题
完形填空

You are a German living in Berlin. One day you’ re walk¬ing down the street, minding your own business, when sudden¬ly a stranger comes up with a smile on his face. After stopping you, he holds a small electronic device (装置) close to his face and speaks slowly into it, saying, in English," Can you tell me where I can buy some sauerkraut?" What should you do? (a) Run away; (b) Call the police; or (c) Listen closely for the device to say in German," Konnen Sie mir bitte sagen, welches sauerkraut haufen kann?"

The most proper answer would be (c) because the person in front of you is only a tourist trying to enjoy himself. The de¬vice is said to be the world’s first portable(便携的) translator — a hand-held microcomputer that at the same time translates one spoken language into another. The four-pound, battery-op¬erated product is called the Voice, and it is the invention of Advanced Products and Technologies, an American electronics company. When the Voice is introduced in the Unite States in late April — at a price of (1,500 — it will be used to trans¬late spoken English into Italian, German, French and Span¬ish. The product comes with separate cartridges(盒式存储器) for each of the four languages, which can be changed when the user travels from one country to another. It will be sold in Eu¬rope soon after the US introduction, with cartridges that trans¬late Italian, German, French and Spanish into English.

The Voice uses a microchip(微型集成电路片) to trans¬late languages. It is Started by voice command and produces voice output through a built-in speaker. When the user makes a statement or asks a question, the Voice immediately repeats what has been said in another language.

1. The device held by the stranger is probably a kind of________.

A. a two-way radio                      B. language translator

C. easily-carried speaker                     D. a multi-functioned computer

2. What does the last sentence of the first paragraph mean?

A. Can you tell me where I can buy some sauerkraut?

B. Can I ask for some information from the police?

C. Would you like to try my device?

D. Would you not run away if I ask you where to buy some sauerkraut?

3. When the stranger says," Can you tell... sauerkraut?" he is ________.

A. learning German from his device

B. asking you the way to the sauerkraut shop

C. making fun of you with his device

D. testing his device for fun

4. Which of the following is not mentioned in the text?

A. The price of the hand-held microcomputer.

B. The function of the product Voice.

C. The producer pf the small electronic device.

D. The number of the device sold to the European coun¬tries.