2018福州初三物理质检试题及答案

九年级物理答案——（共2页）12018年福州市初中毕业班质量检测物理试卷参考答案及评分标准一、选择题：本题共16小题，每小题2分，共32分。在每小题给出的四个选项中，只有一项是符合题目要求的。1.D2.B3.A4.D5.B6.A7.C8.A9.B10.C11.C12.D13.B14.D15.C16.B二、填空题：本题共6小题，每空1分，共12分。17.音色空气18.无规则反射19.电裂变20.75%不变21.不变不变22.1∶31∶2三、作图题：本题共2小题。每小题2分，共4分。23.如答图1所示24.如答图2所示四、简答题：本题共1小题。共4分。25.（1）家庭电路中电流过大的原因：①短路；②用电器总功率过大（也称为负载过大）；（2）根据焦耳定律Q=I2Rt，在通电时间t和电阻R不变情况下，电流I越大，电线产生的热量Q就越多，所以容易引起火灾。五、实验题：本题共5小题。共28分。26.(5分)⑴99⑵热传递⑶液化⑷99小于27.(8分)⑴如答图3⑵断开B⑶灯断路⑷A2.50.30.7528.(5分)⑴①10②缩小③放大镜⑵远离⑶3029.(5分)⑴右⑵2⑶变大⑷②OC的长度为l3③l2ρ水l2-l330.(5分)⑴3.5⑵如答图4(2分)⑶1.5⑷弹簧片的长度（厚度、宽度、材料等）答图2答图4答图1答图2九年级物理答案——（共2页）2六、计算题：本题共3小题。共20分。31.(5分)解：⑴Q放=Vq=Vnq天然气=1m3×164×4.2×107J/m3=6.888×109J··················································································2分⑵由Q吸=cmΔt得：m=Q吸cΔt=Q放cΔt=6.888×109J4.2×103J/(kg·℃)×(70℃－20℃)=3.28×104kg···················································································3分32.(7分)解：⑴v=72km/h=20m/s，t=10min=600s由v=st得：s=vt=20m/s×600s=1.2×104m···································································2分⑵W=UIt=300V×100A×600s=1.8×107J························································································2分⑶水平匀速直线运动∴F=f=1350NW有用=Fs=1350N×1.2×104m=1.62×107Jη=W有用W总×100%=W有用W×100%=1.62×107J1.8×107J×100%=90%···································3分33.(8分)解：R1、R2、R3串联，电压表V1测U2+U3，电压表V2测U3⑴当滑片在a端时，R2=0，电流达到最大值由图像可知，此时I=0.3A······································································1分⑵R3=U3I=1.5V0.3A=5Ω···············································································3分⑶由图像得：U=4.5V+0.1A·R1R1=15ΩU=1.5V+0.3A·R1U=6V··························································2分滑片在b端时，I′=0.1AP=I′2R1=（0.1A）2×15Ω=0.15W·······························································2分解得