7. Very few ___ his address in the town.
a. has known b. are knowing c. know d. knows
6. Twenty miles ___ a long way to cover.
a. seem to be b. is c. are d. were
5. Nine plus three ___ twelve.
a. are making b. is making c. make d. makes
4. There are two roads and either ___ to the station.
a. is leading b. are leading c. lead d. leads
3. My father, together with some of his old friends, ___ there already.
a. will be b. had been c. has been d. have been
2. My family as well as I ___ glad to see you.
a. was b. is c. are d. am
1. Neither he nor I ___ for the plan.
a. were b. is c. are d. am
31.(4分)在研究“電磁鐵的磁性強弱跟什么因素有關(guān)”時，小華和小杰從實驗室選取了匝數(shù)分別為50匝和100匝的外形相同的電磁鐵，并先后將這兩個電磁鐵接入電路中，如圖所示.閉合開關(guān)S后用電磁鐵吸引大頭針，并移動滑動變阻器的滑片P重復了多次實驗，記錄如下：
|
線圈匝數(shù) |
50 |
100 |
||||
|
實驗次數(shù) |
1 |
2 |
3 |
4 |
5 |
6 |
|
電流表示數(shù)/A |
1.0 |
1.3 |
1.6 |
1.0 |
1.3 |
2.0 |
|
吸引大頭針的最多數(shù)目/枚 |
10 |
16 |
25 |
20 |
32 |
50 |
(1)實驗中，可通過觀察____來判定電磁鐵的磁性強弱.
(2)分析第1、4次和2、5次的實驗可得出結(jié)論：在____相同的情況下，線圈的匝數(shù)越____磁性越強.
(3)分析第4、5、6次的實驗記錄，可得出結(jié)論：____.
30.(9分)在測定額定電壓為“2.5V”小燈泡電功率的實驗中：
(1)完成實物圖的連接
(2)開關(guān)閉合前，將變阻器的阻值調(diào)到最大是為了____.
(3)檢查電路連接無誤后，閉合開關(guān)發(fā)現(xiàn)燈泡不亮，電壓表有示數(shù)，電流表無示數(shù)，造成這種故障的原因是____.
(4)排除故障后，得到如下實驗數(shù)據(jù)，請根據(jù)數(shù)據(jù)完成實驗表格：
|
實驗次數(shù) |
燈泡兩端電壓U/V |
通過燈泡電流I/A |
燈泡的功率P/W |
燈泡明暗情況 |
|
1 |
1.5 |
0.2 |
0.3 |
較暗 |
|
2 |
2.5 |
0.3 |
|
正常發(fā)光 |
|
3 |
3 |
0.32 |
|
較亮 |
(5)測完功率后又算出小燈泡在不同電壓下的電阻值，發(fā)現(xiàn)電壓升高時電壓____(選填“變大”、“變小”或“不變”)，其主要原因是____.
29.(6分)如圖所示，石塊的質(zhì)量為____g，在乙圖中石塊受到的浮力為____N，在丙圖中彈簧測力計的示數(shù)為____N，石塊的體積為____cm3，密度為____g/cm3，如果按圖乙甲的順序測量石塊的密度，結(jié)果會____(選填“偏大”、“偏小”或“無影響”).(g取10N/kg)
湖北省互聯(lián)網(wǎng)違法和不良信息舉報平臺 | 網(wǎng)上有害信息舉報專區(qū) | 電信詐騙舉報專區(qū) | 涉歷史虛無主義有害信息舉報專區(qū) | 涉企侵權(quán)舉報專區(qū)
違法和不良信息舉報電話：027-86699610 舉報郵箱：58377363@163.com