某班同学做“用滑动变阻器改变电流”的实验，电路如图所示． ⑴_爱下问搜题

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问题实验题

某班同学做“用滑动变阻器改变电流”的实验，电路如图所示．

⑴连接实物时，开关应当，滑片P应移动最端（选填“左”或“右”）；

⑵开始实验后，甲同学发现无论怎样移动滑片P，灯的亮度都不发生变化，而且一直很暗，这可能是；乙同学发现无论怎样移动滑片P，灯一直很亮，这可能是；丙同学缓慢移动滑片P时，看到灯忽然亮又忽然不亮这可能是．

答案

断开右导线与滑动变阻器下端两接线柱连接导线与滑动变阻器上端两接线柱连接滑动变阻器滑片接触不良

题目分析：连接实物时，开关应该是断开的；滑动变阻器应达到阻值最大处，图中滑片应移动到右端；开始实验后，甲同学发现无论怎样移动滑片P，灯的亮度都不发生变化，而且一直很暗，这可能是导线与滑动变阻器下端两接线柱连接，阻值较大；乙同学发现无论怎样移动滑片P，灯一直很亮，这可能是导线与滑动变阻器上端两接线柱连接，电路中的电阻较小；看到灯忽然亮又忽然不亮这可能是滑动变阻器滑片接触不良。

点评：解决本题的根据是熟知滑动变阻器的连接方式

问答题论述题

试述行波学说。

阅读理解

Honey Sweet Cake(Prep. Time: 12 mins.)
Ingredients
Strawberries in syrup(糖浆), 1 package(unfrozen)
Heavy cream, 1 cup
Corn flour, 2 tablespoons
Process
Mix the strawberries, cream and corn flour in a saucepan. Cook over medium heat for about 8～10 minutes, while constantly mixing until the mixture thickens. Remove from heat and refrigerate for two hours. Fill the frozen mixture in cake, and serve.

Rosy Cake(Prep. Time: 10 mins.)
Ingredients
Sugar, cup
Water, 1 cup
Corn flour, 3 tablespoons
Strawberries, 2～3 cups
Process
Take a large saucepan and mix all the ingredients. Cook until the mixture thickens over medium heat. Let it cool naturally and completely. Fill up your cake with the mixture, and serve.

Triangle Sweet(Prep. Time: 15 mins.)
Ingredients
Sugar, cup
Whipping cream, cup
Unflavoured gelatin(明胶), 1 tablespoon
Cold water, 2 tablespoons
Boiled water, 3 tablespoons
Strawberries crushed, 2 cups
Process
Add sugar to the crushed strawberries and set them aside. In cold water, soften gelatin, and once it is softened, add boiling water. Stir(搅动) until the gelatin dissolves(溶解)．Add the dissolved gelatin mixture to the strawberries and let it cool. Now whip(搅打) the cream till it becomes stiff. When the strawberry mixture is of syrup thickness, add the whipped cream to it. Refrigerate until it sets. Fill it into your cake, and serve.

Flaming Maple(Prep. Time: 10 mins.)
Ingredients
Fresh lemon juice, 1 tablespoons
Honey, 2 tablespoons
Maple syrup, 2 tablespoons
Strawberries, ripe, 2 pints
Process
Make a fruit butter of half of the strawberries. Add honey, lemon juice, and maple syrup until it forms a smooth sauce. Add the remaining strawberries. Fill the mixture in the cake, and serve.

小题1:Which of the following ingredients (is) are used in all the recipes?

A．Heavy cream.	B．Sugar syrup.
C．Corn flour.	D．Strawberries.

小题2:Chefs needn't freeze the ingredients when preparing ________．
① Honey Sweet Cake ② Rosy Cake ③Triangle Sweet ④Flaming Maple

小题3:Which of the following is TRUE?

A．Triangle Sweet takes the longest time to prepare.

B．Strawberries used in the recipes aren't all fresh.

C．Most strawberries are used when making a Rosy Cake.

D．Honey Sweet Cake is the best choice for busy mothers.

小题4:In how many recipes should chefs thicken the mixture by heating?