问题 选择题

在图所示电路中,电源电动势为12V,电源内阻为l.0Ω,电路中的电阻R0为1.5Ω,小型直流电动机M的内阻为0.5Ω,闭合开关S后,电动机转动,电流表的示数为2.0A.则以下判断中正确的是(  )

A.电动机的输出功率为14W

B.电动机两端的电压为7.0V

C.电动机产生的热功率4.0W

D.电源输出的电功率为24W

答案

B、电路中电流表的示数为2.0A,所以电动机的电压为U=E-U-UR0=12-Ir-IR0=12-2×1-2×1.5=7V,所以B正确;

A、C,电动机的总功率为P=UI=7×2=14W,电动机的发热功率为P=I2R=22×0.5=2W,所以电动机的输出功率为14 W-2W=12W,所以A、C错误;

D、电源的输出的功率为P输出=EI-I2R=12×2-22×1=22W,所以D错误.

故选B.

完形填空

阅读下面短文,按照句子结构的语法性和上下文连贯的要求,在空格处填入一个适当的词或使用括号中词语的正确形式填空,并将答案填写在答题卡标号为16—25的相应位置上。

Ms. Mary was over eighty, but she still drove her old car like half her age. She loved driving very fast, and boasted of the fact   16.          she had never, in her thirty-five years of driving, been punished  17.          a driving mistake.

Then one day, she nearly lost her record. A police car followed her, and the policemen in it saw her pass a red light without  18.          (stop).

When Ms. Mary came before the judge, he looked at her severely and said that she was too old to drive a car, and that the reason  19.                    she had not stopped at red light was most probably that her eyes had become weak        20            old age, so that she had simply not seen it.

When the judge had finished  21.           he was saying, Ms. Mary opened the big handbag she was carrying and took out her sewing. Without saying a word, she  22.              (choose) a needle with a very small eye, and threaded it at the first time.

When she had  23               (success) done this, she took the thread out of the needle again and handed both the needle and thread to the judge, saying, “Now it is your turn. I suppose you can drive a car well, and you have no doubts   24.          your eyesight.”

The judge took the needle and tried to thread it. After half a dozen times, he had still not succeeded. The case against Ms. Mary  25.         (dismiss), and her record remained unbroken.

多项选择题

已知数据文件IN26.DAT中存有200个4位数,并已调用读函数readDat()把这些数存入数组a中。请编制一函数jsVal(),其功能是:把千位数字和个位数字重新组成一个新的十位数(新十位数的十位数字是原4位数的千位数字,新十位数的个位数字是原4位数的个位数字),把百位数字和十位数字组成另一个新的十位数(新十位数的十位数字是原4位数的百位数字,新十位数的个位数字是原4位数的十位数字),如果新组成的两个十位数均是奇数并且两个十位数中至少有一个数能被5整除,同时两个新十位数字均不为零,则将满足此条件的4位数按从大到小的顺序存入数组b中,并要求计算满足上述条件的4位数的个数cnt,最后调用写函数writeDat(),把结果cnt及数组b中符合条件的4位数输出到OUT26.DAT文件中。
注意:部分源程序已给出。
程序中已定义数组:a[200],b[200],已定义变量:cnt。
请勿改动主函数main()、读函数readDat()和写函数writeDat()的内容。
试题程序:
#include 〈stdio.h>
#define MAX 200
int a[MAX], b[MAX], cnt = 0; void jsVal()

void readDat()

int i;
FILE *fp;
fp = fopen("IN26.DAT", "r");
for(i = 0; i 〈 MAX; i++)
fscanf(fp, "%d", &a[i]);
fclose (fp);
main ( )

int i;
readDat ();
jsVal ();
printf("满足条件的数=%d\n", cnt);
for(i = 0; i 〈 cnt; i++)
printf("%d ", b[i]);
printf ("\n");
writeDat ();
writeDat ()

FILE *fp;
int i;
fp = fopen("OUT26.DAT", "w");
fprintf(fp, "%d\n", cnt);
for(i = 0; i 〈 cnt; i++)
fprintf(fp, "%d\n", b[i]);
fclose (fp);