搜题请搜索小程序“爱下问搜题”
问题 选择题

某电池当外电路断开时的路端电压为3 V，接上8 Ω的负载电阻后其路端电压为2.4 V，则可以判定该电池的电动势E和内电阻r为

A．E＝2.4 V，r＝1 Ω

B．E＝3 V，r＝2 Ω

C．E＝2.4 V，r＝2 Ω

D．E＝3 V，r＝1 Ω

答案

答案：B

本题考查了对闭合回路电路的简单计算，利用公式解题

因为当外电路断路时，路端电压等于电源电动势，所以，接上8 Ω的负载电阻后其路端电压为2.4 V，可得此时电路的电流为，所以由闭合回路的欧姆定律可得，解得，B正确，

思路拓展：当在解答闭合回路的计算时，根据题中的信息，分别列出等式，然后联立方程求解，另外还需明白当外电路断路时，R无穷大，I为零，即路端电压等于电源电动势，当外电路短路时，R为零，表示短路电流，

单项选择题

对于货币型理财产品，以下描述错误的是（）。

A.主要投资于货币市场的银行理财产品

B.投资期短，资金赎回灵活

C.收益安全性高

D.保障本金
查看答案
单项选择题

Section Ⅰ Use of English Directions: Read the following text. Choose the best word (s) for each numbered blank and mark A, B, C or D on ANSWER SHEET 1. (10 Points) A scientist who does research in economic psychology and who wants to predict the way in which consumers will spend their money must study consumer behavior. He must obtain (1) both on resources of consumers and on the motives that (2) to encourage or discourage money spending. If an (3) were asked which of three groups borrow most -- people with rising incomes, (4) incomes, or declining incomes -- he would (5) answer: those with declining incomes. Actually, in the years 1997 -2000, the answer was: people with rising incomes. People with declining incomes were next and people with stable incomes borrowed the (6) . This shows us that tradition- al (7) about earning and spending are not always (8) Another traditional assumption is that if people who have money expect prices to go up, they will (9) to buy. If they expect prices to go down, they will postpone buying. (10) research surveys have shown that this is not always (11) The expectations of price increases may not stimulate buying. One (12) attitude was ex- pressed by the wife of a mechanic in an interview at a time of rising prices. Her family had been planning to buy a new car but they postponed this purchase. (13) , the rise in prices that has al- ready taken place may be resented and buyer’s resistance may be evoked. The (14) mentioned above was carried out in America. Investigations (15) at the same time in Great Britain, however, yielded results that were more (16) traditional assumptions about saving and spending patterns. The condition most contributive to spending (17) to be price stability. If prices have been stable and people consider that they are (18) , they are likely to buy. Thus, it appears that the common (19) policy of maintaining stable prices is based on a correct understanding of (20) psychology.

Read the following text. Choose the best word (s) for each numbered blank and mark A, B, C or D on ANSWER SHEET 1.19（）

A．appears

B．occurs

C．happens

D．expects
查看答案