CIE AS ALevel Paper3 物理2020年真题 实验题
2020年全国卷Ⅲ理综物理高考试题(含答案)
绝密★启用前2020年普通高等学校招生全国统一考试理科综合能力测试注意事项：1.答卷前，考生务必将自己的姓名、准考证号填写在答题卡上。
2.回答选择题时，选出每小题答案后，用铅笔把答题卡上对应题目的答案标号涂黑，如需改动，用橡皮擦干净后，再选涂其它答案标号。
回答非选择题时，将答案写在答题卡上，写在本试卷上无效。
3.考试结束后，将本试卷和答题卡一并交回。
二、选择题：本题共8小题，每小题6分，共48分。
在每小题给出的四个选项中，第14~18题只有一项符合题目要求，第19~21题有多项符合题目要求。
全部选对的得6分，选对但不全的得3分，有选错的得0分。
14.如图，水平放置的圆柱形光滑玻璃棒左边绕有一线圈，右边套有一金属圆环。
圆环初始时静止。
将图中开关S由断开状态拨至连接状态，电路接通的瞬间，可观察到制口%」A.拨至M端或N端，圆环都向左运动B.拨至M端或N端，圆环都向右运动C.拨至M端时圆环向左运动，拨至N端时向右运动D.拨至M端时圆环向右运动，拨至N端时向左运动15.甲、乙两个物块在光滑水平桌面上沿同一直线运动，甲追上乙，并与乙发生碰撞，碰撞前后甲、乙的速度随时间的变化如图中实线所示。
已知甲的质量为 1 kg,则碰撞过程两物块损失的机械能为梦想不会辜负每一个努力的人“嫦娥四号”探测器于 2019年1月在月球背面成功着陆，着陆前曾绕月球飞行，某段时间可认为绕月为a 和自若行70° ,则真空中有一匀强磁场， 磁场边界为两个半径分别为 a 和3a 的同轴圆柱面，磁场的方向与圆柱轴线平行,其横截面如图所示。
一速率为 v 的电子从圆心沿半径方向进入磁场。
已知电子质量为 忽略重力。
为使该电子的运动被限制在图中实线圆围成的区域内，磁场的磁感应强度最小为R 2、R 3均为固定电阻，R 2=10 , R 3=20 ,各电表均为理想电表。
已知电阻 R 2中电流i 2随时间t16. A. 3 JB. 4 JC. 5 JD. 6 J做匀速圆周运动，圆周半径为月球半径的 K 倍。
2020高中物理 第一章 碰撞与动量守恒 章末过关检测(含解析)教科版-5
章末过关检测（时间：90分钟,满分：100分）一、选择题(本题共8小题,每小题6分，共48分。
1～5题为单项选择题，6～8题为多项选择题．全部选对的得6分,选对但不全的得3分，有选错的得0分)1．某物体受到一个－6 N·s的冲量作用，则（)A．物体的动量一定减小B．物体的末动量一定是负值C．物体动量增量的方向一定与规定的正方向相反D．物体原来动量的方向一定与这个冲量的方向相反解析:根据动量定理知合外力的冲量等于动量的变化量,动量定理为矢量式，合外力冲量的方向与动量变化量的方向相同,冲量的方向为负方向说明动量的增量方向与规定的正方向相反，所以C项正确；动量的增量为负值，有可能物体的末动量方向为负方向，所以A项错误；若物体的末动量比初动量小，动量的变化量就为负值，所以B项错误;正方向的规定是人为的,与物体原来动量的方向可以相同也可以不同，所以D项错误．答案:C2．在不计空气阻力作用的条件下,下列说法中不正确的是( ) A．自由下落的小球在空中运动的任意一段时间内，其增加的动能一定等于其减少的重力势能B．做平抛运动的小球在空中运动的任意相同的时间内，其速度的变化量一定相同C．做匀速圆周运动的小球在任意一段时间内其合外力做的功一定为零，合外力的冲量也一定为零D．单摆在一个周期内，合外力对摆球做的功一定为零，合外力的冲量也一定为零解析:不计空气阻力，自由下落的小球，其所受合外力为重力，则小球在运动的过程中机械能守恒，其增加的动能一定等于其减小的重力势能，故A正确；做平抛运动的小球所受合外力为重力，加速度的大小与方向都不变，所以小球在空中运动的任意相同的时间内，其速度的变化量一定相同，故B正确;做匀速圆周运动的小球，其所受合外力的方向一定指向圆心，小球在任意一段时间内其合外力做的功一定为零，但由于速度的方向不断变化，所以速度的变化量不一定等于0，合外力的冲量也不一定为零，故C错误；经过一个周期，单摆的小球又回到初位置，所有的物理量都与开始时相等,所以单摆在一个周期内，合外力对摆球做的功一定为零,合外力的冲量也一定为零，故D正确．答案:C3．在光滑水平面上，一质量为m、速度大小为v的A球与质量为2m静止的B球碰撞后，A球的速度方向与碰撞前相反，则碰撞后B 球的速度大小可能是( )A．0。
2020年高考物理一轮复习：54 实验：测定玻璃的折射率
2020年高考物理一轮复习：54 实验：测定玻璃的折射率姓名:________ 班级:________ 成绩:________一、多选题 (共1题；共3分)1. （3分） (2019高二下·厦门期中) 在用插针法测定玻璃砖的折射率的实验中，甲、乙、丙三位同学在纸上画出的界面与玻璃砖位置的关系分别如图①、②和③所示，其中甲、丙两同学用的是矩形玻璃砖，乙同学用的是梯形玻璃砖。
他们的其他操作均正确，且均以aa′、bb′为界面画光路图。
以下说法正确的是：____________（本题为多选题，漏选、错选均不得分）A . 甲同学测得的折射率与真实值相比一定偏大B . 甲同学测得的折射率与真实值相比一定偏小C . 乙同学测得的折射率与真实值相比一定偏大D . 乙同学测得的折射率与真实值相比一定偏小E . 丙同学测得的折射率与真实值相比可能偏大F . 丙同学测得的折射率与真实值相比可能偏小二、实验探究题 (共11题；共39分)2. （3分）某同学用插针法测量半圆形的玻璃砖的折射率，实验步骤如下：①首先在白纸上画一条直线aa′，再画一条入射光线AO．②然后把半圆形的玻璃砖放在白纸上，使平界面与直线aa′对齐，且使其圆心与O点对齐．③在AO上间隔一定距离竖直地插上2枚大头针P1、P2 ．（1）在半圆形的玻璃砖的圆形侧插上第三枚大头针P3，使其同时挡住________．（2）画出完整的光路图．（3）对你画出的光路图进行测量和计算，求得该玻璃砖的折射率n=________（保留3位有效数）3. （2分）如图所示，在做《测定玻璃砖的折射率》的实验时，提供的实验器材是：两对面平行的玻璃砖一块，大头针四枚，白纸一张，直尺一把．部分实验操作步骤如下：①先在白纸上画出一条直线EE′，代表两种介质的分界面；再画出一直线段AB代表入射光线；然后画出分界面上B点处的法线．②把长方形玻璃砖放在白纸上，使它的一个长边与EE’对齐，然后用笔沿着玻璃砖的面画出直线FF’．③在直线AB上竖直地插上两枚大头针G1、G2 ，然后透过玻璃砖观察大头针G1、G2的像，调整视线方向，直到G1的像被G2挡住．④再在观察的这一侧竖直地插上两枚大头针G3、G4 ，用G3挡住G1和G2的像，用G4挡住G3以及G1、G2的像．⑤移去大头针和玻璃砖，过G3、G4的插点画直线CD，与FF’相交于C点，画出直线BC．（1）还缺少的器材是________．（2）上述操作中有一处错误，这个错误出现在步骤________中．（填写步骤序号）（3）某同学在用“插针法”测定一块矩形玻璃砖的折射率时，在纸上画出的界面aa'和bb'与玻璃砖的位置关系如图所示，他的其他操作均正确，则他测得的折射率与真实值相比________．（填“偏大”或“偏小”）4. （2分） (2017高二下·邯郸期末) 如图甲，长方形玻璃砖的上下表面是磨砂面，前侧面是光学面，后侧面是镀银面，前后面间的距离为d，现用圆规和直尺测定其折射率，主要操作如下（俯视图如图乙）A．在木板上固定一张白纸，在白纸上画一条直线ab，并在适当位置作ab的垂线ONB．利用圆规和直尺作∠aON角平分线AOC．在AO上的适当位置竖直固定两枚大头针P1、P2D．放上玻璃砖，使光学面的底线与ab重合E．通过光学面观察P1、P2经镀银面成的像，并在视线上插一枚大头针P3 ，使P3挡在P1、P2的像；再插一枚大头针P4 ，使P4挡住P3及P1、P2的像F．连接P4P3并延长与ab相交于O1 ．（1）P4、P3连线与直线ab的夹角为θ=________．（2）若测得O、O1间的距离为l，则该玻璃砖的折射率可表示为n=________．（3）若操作中玻璃砖的实际位置没有与ab重合，而位于ab的后方（图中的虚线处），则测得的折射率比真实值________（填“偏大”、“偏小”或“不变”）．5. （2分） (2019高二下·元坝期中) 如图所示，某同学用插针法测定一半圆形玻璃砖的折射率．在平铺的白纸上垂直纸面插大头针P1、P2确定入射光线，并让入射光线过圆心O ，在玻璃砖(图中实线部分)另一侧垂直纸面插大头针P3 ，使P3挡住P1、P2的像，连接OP3 ，图中MN为分界线，虚线半圆与玻璃砖对称，B、C分别是入射光线、折射光线与圆的交点，AB、CD均垂直于法线并分别交法线于A、D点．（1）设AB的长度为l1，AO的长度为l2，CD的长度为l3，DO的长度为l4，为较方便地表示出玻璃砖的折射率，需用刻度尺测量________，则玻璃砖的折射率可表示为________．（2）该同学在插大头针P3前不小心将玻璃砖以O为圆心顺时针转过一小角度，由此测得玻璃砖的折射率将________(选填“偏大”“偏小”或“不变”)．6. （7分）用“插针法”测一块两面不平行的玻璃砖的折射率．（1）下列操作应该在将玻璃砖放在白纸上之前完成的有．A . 在白纸上画一条直线代表空气与玻璃的一个界面B . 在白纸上画两条直线代表空气与玻璃的两个界面C . 画一条线段代表入射光线D . 画一条线段代表折射光线E . 画一条线段代表光线透过玻璃砖后的传播路径（2）放好玻璃砖，在玻璃砖的一侧的合适位置插上两枚大头针P1和P2，然后在玻璃砖的另一侧观察，调整视线使P2挡住P1的像；接着在眼睛所在的一侧插上两枚大头针P3，P4，使________挡住________的像，________挡住________的像．P1、P2、P3、P4在纸上的位置如图所示，虚线代表玻璃砖的四个面．①在图上将实验所需的图补充完整________；②测量工具是量角器，为了测出玻璃砖的折射率，需要测量的物理量是________，③计算折射率的公式n=________．（要求用②中测得的物理量表示）7. （4分）(2020·莆田模拟) 某同学用“插针法”测一玻璃砖的折射率。
2020年全国普通高等学校招生高考物理压轴试卷(全国卷Ⅲ) (含答案解析)
2020年全国普通高等学校招生高考物理压轴试卷(全国卷Ⅲ)一、单选题（本大题共5小题，共30.0分）1.下列说法正确的是()A. 卢瑟福根据天然放射现象提出了原子的核式结构B. 一个氢原子从n=3的能级跃迁到n=2的能级，吸收光子，能量增加C. 铀( 92238U)经过多次α、β衰变形成稳定的铅( 82206Pb)的过程中，有6个中子转变成质子D. 机场、车站等地进行安全检查时，能轻而易举地窥见箱内物品，利用了γ射线较强的穿透能力2.a、b、c、d是在地球大气层外的圆形轨道上运行的四颗人造卫星．其中a、c的轨道相交于P，b、d在同一个圆轨道上，b、c轨道在同一平面上．某时刻四颗卫星的运行方向及位置如图示．下列说法中正确的是()A. a、c的加速度大小相等，且大于b的加速度B. b、c的角速度大小相等，且小于a的角速度C. a、c的线速度大小相等，且小于d的线速度D. a、c存在在P点相撞危险3.如图，理想变压器原、副线圈分别接有额定电压相同的灯泡a和b.当输入电压U为灯泡额定电压的10倍时，两灯泡均能正常发光．下列说法正确的是()A. 原、副线圈匝数之比为9：1B. 原、副线圈匝数之比为1：9C. 此时a和b的电功率之比为9：1D. 此时a和b的电功率之比为1：104.一倾角为30°的斜劈放在水平地面上，一物体沿斜劈匀速下滑．现给物体施加如图所示力F，F与竖直方向夹角为30°，斜劈仍静止，物体加速下滑，则此时地面对斜劈的摩擦力为()A. 大小为零B. 方向水平向右C. 方向水平向左D. 无法判断大小和方向5.一物体竖直向下匀加速运动一段距离，对于这一运动过程，下列说法正确的是()A. 物体的机械能一定增加B. 物体的机械能一定减少C. 相同时间内，物体动量的增量一定相等D. 相同时间内，物体动能的增量一定相等二、多选题（本大题共5小题，共27.0分）6.某物体运动的v−t图象如图所示，下列说法正确的是()A. 物体在第1s末运动方向发生改变B. 物体在第2s内和第4s内的加速度是相同的C. 物体在第4s末返回出发点D. 物体在第5s时离出发点最远，且最大位移为0.5m7.如图所示，一根阻值为R的金属导体棒从图示位置ab分别以v1、v2的速度沿光滑导轨(电阻不计)匀速滑到a′b′位置，若v1∶v2=1∶2，则在这两次过程中说法正确的是()A. 回路电流I1∶I2=1∶2B. 产生的热量Q1∶Q2=1∶4C. 通过任一截面的电荷量q1∶q2=1∶1D. 外力的功率P1∶P2=1∶28.如图，光滑固定斜面的倾角为30°，A、B两物体的质量之比为5：1.B用不可伸长的轻绳分别与A和地面相连，开始时A、B离地高度相同。
CIE数学9709 2020 三月真题paper1
*1939478240*Cambridge International AS&A LevelCANDIDATENAMECENTRENUMBERCANDIDATENUMBERMATHEMATICS9709/12 Paper1Pure Mathematics1February/March20201hour50minutes You must answer on the question paper.You will need:List of formulae(MF19)This document has20pages.Blank pages are indicated.JC2003_9709_12/FP©UCLES2020[Turn over1 1The function f is defined by f x =2The graph of y=f x is transformed to the graph of y=1+f 13xyThe diagram shows part of the curve with equation y =x 2+1.The shaded region enclosed by the curve,the y -axis and the line y =5is rotated through 360 about the y -axis .Find the volume obtained.[4]................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................©UCLES 20209709/12/F/M/204A curve has equation y=x2−2x−3.A point is moving along the curve in such a way that at P the y-coordinate is increasing at4units per second and the x-coordinate is increasing at6units per second.Find the x-coordinate of P.[4] ................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................©UCLES20209709/12/F/M/20[Turn over5Solve the equationtan +3sin +26The coefficient of 1x25is720.(a)Find the possible values of the constant a.[3]........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(b)Hencefind the coefficient of17O ABThe diagram shows a sector AOB which is part of a circle with centre O and radius 6cm and with angle AOB =0.8radians.The point C on OB is such that AC is perpendicular to OB .The arc CD is part of a circle with centre O ,where D lies on OA .Find the area of the shaded region.[6]................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................©UCLES 20209709/12/F/M/208A woman’s basic salary for herfirst year with a particular company is$30000and at the end of the year she also gets a bonus of$600.(a)For herfirst year,express her bonus as a percentage of her basic salary.[1]................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................At the end of each complete year,the woman’s basic salary will increase by3%and her bonus will increase by$100.(b)Express the bonus she will be paid at the end of her24th year as a percentage of the basic salarypaid during that year.[5] ................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................©UCLES20209709/12/F/M/20[Turn over9(a)Express2x2+12x+11in the form2 x+a 2+b,where a and b are constants.[2] ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................The function f is defined by f x =2x2+12x+11for x≤−4.(b)Find an expression for f−1 x and state the domain of f−1.[3]................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................©UCLES20209709/12/F/M/20The function g is defined by g x =2x−3for x≤k.(c)For the case where k=−1,solve the equation fg x =193.[2]................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(d)State the largest value of k possible for the composition fg to be defined.[1]................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................10The gradient of a curve at the point x,y is given by d y2−x.The curve has a stationarypoint at a,14 ,where a is a positive constant.(a)Find the value of a.[3]................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(b)Determine the nature of the stationary point.[3]........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(c)Find the equation of the curve.[4]........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................。
2020年全国普通高等学校招生统一考试物理试卷 (全国Ⅲ卷)
2020年全国普通高等学校招生统一考试物理试卷（全国Ⅲ卷）一、单选题1.如图，水平放置的圆柱形光滑玻璃棒左边绕有一线圈，右边套有一金属圆环。
圆环初始时静止。
将图中开关S由断开状态拨至连接状态，电路接通的瞬间，可观察到( )A．拨至M端或N端，圆环都向左运动B．拨至M端或N端，圆环都向右运动C．拨至M端时圆环向左运动，拨至N端时向右运动D．拨至M端时圆环向右运动，拨至N端时向左运动2.甲、乙两个物块在光滑水平桌面上沿同一直线运动，甲追上乙，并与乙发生碰撞，碰撞前后甲、乙的速度随时间的变化如图中实线所示。
已知甲的质量为1 kg，则碰撞过程两物块损失的机械能为( )A.3 JB.4 JC.5 JD.6 J3.“嫦娥四号”探测器于2019年1月在月球背面成功着陆，着陆前曾绕月球飞行，某段时间可认为绕月做匀速圆周运动，圆周半径为月球半径的K倍。
已知地球半径R是月球半径的P倍，地球质量是月球质量的Q倍，地球表面重力加速度大小为g。
则“嫦娥四号”绕月球做圆周运动的速率为（）RKg QP RPKgQRQgKPRPgQK4.如图，悬挂甲物体的细线拴牢在一不可伸长的轻质细绳上O点处；绳的一端固定在墙上，另一端通过光滑定滑轮与物体乙相连。
甲、乙两物体质量相等。
系统平衡时，O 点两侧绳与竖直方向的夹角分别为α和β。
若70α=°，则β等于（ ）A.45°B.55°C.60°D.70°5.真空中有一匀强磁场，磁场边界为两个半径分别为a 和3a 的同轴圆柱面，磁场的方向与圆柱轴线平行，其横截面如图所示。
一速率为v 的电子从圆心沿半径方向进入磁场。
已知电子质量为m ，电荷量为e ，忽略重力。
为使该电子的运动被限制在图中实线圆围成的区域内，磁场的磁感应强度最小为（ ）A.32mv aeB.mv aeC.34mv aeD.35mv ae二、多选题6.1934年，约里奥—居里夫妇用α粒子轰击铝箔，首次产生了人工放射性同位素X ，反应方程为：42712130He +Al X n +→。
2020学年普通高等学校招生全国统一考试(新课标Ⅲ卷)物理及答案解析
2020年普通高等学校招生全国统一考试（新课标Ⅲ卷）物理一、选择题：本题共8个小题，每题6分，共48分。
在每个小题给出的四个选项中，第1-4题只有一项符合题目要求，第5-8题有多项符合题目要求。
全部选对的得6分，选对不全的得3分，有选错的得0分。
1.（6分）1934年，约里奥﹣居里夫妇用α粒子轰击铝核2713Al ，产生了第一个人工放射性核素X ：α+2713Al→n +X 。
X 的原子序数和质量数分别为( )A.15和28B.15和30C.16和30D.17和31解析：设X 的质量数为m ，电荷数为n ，根据核反应中质量数守恒和电荷数守恒可知： 4+27=1+m ； 2+13=0+n解得：m=30；n=15；故其原子序数为15，质量数为30；故B 正确，ACD 错误。
答案：B2.（6分）为了探测引力波，“天琴计划”预计发射地球卫星P ，其轨道半径约为地球半径的16倍；另一地球卫星Q 的轨道半径约为地球半径的4倍。
P 与Q 的周期之比约为( ) A.2：1 B.4：1 C.8：1 D.16：1解析：根据题意可得P 与Q 的轨道半径之比为： r P ：r Q =4：1根据开普勒第三定律有：32r T =k得：32PP r T =32Q Q r T可得周期之比为：T P ：T Q =8：1故C 正确，ABD 错误。
答案：C3.（6分）一电阻接到方波交流电源上，在一个周期内产生的热量为Q 方；若该电阻接到正弦交流电源上，在一个周期内产生的热量为Q 正。
该电阻上电压的峰值均为u 0，周期均为T ，如图所示。
则Q 方：Q 正等于( )A.1：2B. 2：1C.1：2D.2：1解析：由图可知，方形交流电源的有效值为U 0，故其一周期产生的热量为：Q 方=20U R T ；正弦式交流电的有效值为：U=02故其一周期产生的热量为：Q 正=2U R T=202U T R ；故有：Q 方：Q 正=2：1； 故D 正确，ABC 错误。
2020年高考(全国Ⅲ卷)物理试卷及答案
2020年普通高等学校招生全国统一考试（全国Ⅲ卷）物理试题二、选择题：本题共8小题，每小题6分，共48分。
在每小题给出的四个选项中，第14~18题只有一项符合题目要求，第19~21题有多项符合题目要求。
全部选对的得6分，选对但不全的得3分，有选错的得0分。
14．如图，水平放置的圆柱形光滑玻璃棒左边绕有一线圈，右边套有一金属圆环。
圆环初始时静止。
将图中开关S由断开状态拨至连接状态，电路接通的瞬间，可观察到A．拨至M端或N端，圆环都向左运动B．拨至M端或N端，圆环都向右运动C．拨至M端时圆环向左运动，拨至N端时向右运动D．拨至M端时圆环向右运动，拨至N端时向左运动15．甲、乙两个物块在光滑水平桌面上沿同一直线运动，甲追上乙，并与乙发生碰撞，碰撞前后甲、乙的速度随时间的变化如图中实线所示。
已知甲的质量为1 kg，则碰撞过程两物块损失的机械能为A．3 J B．4 J C．5 J D．6 J16．“嫦娥四号”探测器于2019年1月在月球背面成功着陆，着陆前曾绕月球飞行，某段时间可认为绕月做匀速圆周运动，圆周半径为月球半径的K倍。
已知地球半径R是月球半径的P倍，地球质量是月球质量的Q倍，地球表面重力加速度大小为g．则“嫦娥四号”绕月球做圆周运动的速率为A RKgQPBRPKgQCRQgKPDRPgQK17．如图，悬挂甲物体的细线拴牢在一不可伸长的轻质细绳上O 点处；绳的一端固定在墙上，另一端通过光滑定滑轮与物体乙相连。
甲、乙两物体质量相等。
系统平衡时，O 点两侧绳与竖直方向的夹角分别为α和β。
若α=70°，则β等于A ．45°B ．55°C ．60°D ．70°18．真空中有一匀强磁场，磁场边界为两个半径分别为a 和3a 的同轴圆柱面，磁场的方向与圆柱轴线平行，其横截面如图所示。
一速率为v 的电子从圆心沿半径方向进入磁场。
已知电子质量为m ，电荷量为e ，忽略重力。
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Cambridge International AS & A LevelDC (JC/CT) 182587/3© UCLES 2020[Turn overThis document has 12 pages. Blank pages are indicated.*5745011940*PHYSICS 9702/33Paper 3 Advanced Practical Skills 1 February/March 20202 hoursYou must answer on the question paper.You will need: The materials and apparatus listed in the confidential instructionsINSTRUCTIONS●Answer all questions.●Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.●Write your name, centre number and candidate number in the boxes at the top of the page. ●Write your answer to each question in the space provided. ●Do not use an erasable pen or correction fluid. ●Do not write on any bar codes.●You will be allowed to work with the apparatus for a maximum of 1 hour for each question.●You should record all your observations in the spaces provided in the question paper as soon as theseobservations are made. ●You may use a calculator.●You should show all your working and use appropriate units.INFORMATION●The total mark for this paper is 40.●The number of marks for each question or part question is shown in brackets [ ].For Examiner’s Use 12TotalBLANK PAGE © UCLES 20209702/33/F/M/209702/33/F/M/20© UCLES 2020[Turn overYou may not need to use all of the materials provided.1In this experiment you will investigate the oscillations of a rod.(a)• Assemble the apparatus as shown in Fig. 1.1. •A djust the apparatus until the two springs are approximately 15 cm apart. Each springshould be vertical and the same distance from the middle of the rod. The rod should beparallel to the bench.Fig. 1.1•T he distance between the two springs where they support the rod is x , as shown in Fig. 1.1. Measure and record x .x = ....................................................cm [1](b)•L ift one end of the rod a short distance and push the other end of the rod down a shortdistance. Release the rod so that it oscillates with a rocking motion, as shown in Fig. 1.2.FRONT VIEWFig. 1.2•T ake measurements to determine the period T of the oscillation.T = .......................................................s [2](c) •C hange x by moving the stands. Adjust the apparatus until the springs are vertical andthe rod is parallel to the bench. Measure x and T.•Repeat until you have six sets of values of x and T.•Record your results in a table. Include values of 1x in your table.[9](d) (i) Plot a graph of T on the y-axis against 1x on the x-axis. [3](ii) Draw the straight line of best fit. [1] (iii) Determine the gradient and y-intercept of this line.gradient = ...............................................................y-intercept = ...............................................................[2]9702/33/F/M/20© UCLES 2020© UCLES 2020[Turn over9702/33/F/M/20(e) It is suggested that the quantities T and x are related by the equationT = ax + bwhere a and b are constants.Use your answers in (d)(iii) to determine the values of a and b.Give appropriate units.a = ...............................................................b = ...............................................................[2][Total: 20]9702/33/F/M/20© UCLES 2020You may not need to use all of the materials provided.2 In this experiment you will investigate the magnetic field produced by an electrical current.(a) You are provided with a length of wire wrapped around a plastic channel to form a coil, asshown in Fig. 2.1.other groove)Fig. 2.1Count and record the number N of turns of wire in the coil.N = (1)© UCLES 2020[Turn over9702/33/F/M/20•S lide the compass into the plastic channel so that it is in the middle of the coil.(b)•C onnect the circuit as shown in Fig. 2.2.•R otate the channel on the bench until the arrow of the compass is perpendicular to the channel, as shown.clipFig. 2.2•T he distance between the first and last turns of wire is L, as shown in Fig. 2.2. Measure and record L.L = (1)(c) •C lose the switch. The compass arrow will rotate through an angle θ.•M easure and record θ.θ = .............................................................°•R ecord the ammeter reading I.I = ...............................................................•O pen the switch.[2]© UCLES 20209702/33/F/M/20(d)Estimate the percentage uncertainty in your value of θ.percentage uncertainty = (1)(e) Calculate the value of B usingB = μ0(N−1) ILwhere μ0 = 1.26 × 10–6 N A–2.B = .........................................N A–1 m–1 [1]9702/33/F/M/20© UCLES 2020[Turn over(f) •D isconnect the crocodile clips and remove the compass.•R emove the tape and the wire. Re-wind the wire in adjacent grooves (instead of every other groove), as shown in Fig. 2.3.•Re-fix the tape.Fig. 2.3•R epeat (a), (b), (c) and (e).N = ...............................................................L = ...............................................................θ = .............................................................°I = ...............................................................B = ...............................................N A–1 m–1[3]© UCLES 20209702/33/F/M/209702/33/F/M/20© UCLES 2020[Turn over(g) It is suggested that the relationship between θ and B istan θ = B kwhere k is a constant.(i) Using your data, calculate two values of k .first value of k = ............................................................... second value of k = ............................................................... [1] (ii)Justify the number of significant figures you have given for your values of k . ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [1] (iii)Explain whether your results in (g)(i) support the suggested relationship. ........................................................................................................................................... ........................................................................................................................................... . (1)9702/33/F/M/20© UCLES 2020Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity.To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at after the live examination series.Cambridge Assessment International Education is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of the University of Cambridge Local Examinations Syndicate (UCLES), which itself is a department of the University of Cambridge.(h) (i) Describe four sources of uncertainty or limitations of the procedure for this experiment.1 ...................................................................................................................................................................................................................................................................................2 ...................................................................................................................................................................................................................................................................................3 ...................................................................................................................................................................................................................................................................................4 ........................................................................................................................................ (4)(ii) Describe four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures.1 ...................................................................................................................................................................................................................................................................................2 ...................................................................................................................................................................................................................................................................................3 ...................................................................................................................................................................................................................................................................................4 ........................................................................................................................................ (4)[Total: 20]。