電路如圖1般接駁，假設電池無內阻和伏特計是理想的，如果伏特計度得5V，求電阻R
然後如圖2般重畫，計算得電流=5/4，R=7/(5/4)=28/5。令我有不惑的是，為什麼可把圖1重畫成圖2的樣子??
請見圖:imgur.com/a/YBvZ3 (上方圖為圖1)
一道電路問題求解 請教各位?
2016-06-18 6:47 am
回答 (2)
2016-06-21 4:40 am
Your diagram 2 is WRONG.
In diagram 1, the voltage across the lower-right resistance R is 5v (as shown by the voltmeter). Thus, the voltage across the lower-left resistance R is (12 - 5) v = 7 v. This result shows that the current flowing through the lower-left resistance is larger that that through the lower-right resistance. Hence, there must be current flowing through the 2-ohm resistance (in the upward direction), and a voltage is then established.across it.
But in your diagram 2, there is no current (hence no voltage) across the 2-ohm resistance, because the perfect voltmeter is of infinite resistance. Therefore, diagram 2 has been wrongly drawn. It cannot be used to represent diagram 1.
In diagram 1, the voltage across the lower-right resistance R is 5v (as shown by the voltmeter). Thus, the voltage across the lower-left resistance R is (12 - 5) v = 7 v. This result shows that the current flowing through the lower-left resistance is larger that that through the lower-right resistance. Hence, there must be current flowing through the 2-ohm resistance (in the upward direction), and a voltage is then established.across it.
But in your diagram 2, there is no current (hence no voltage) across the 2-ohm resistance, because the perfect voltmeter is of infinite resistance. Therefore, diagram 2 has been wrongly drawn. It cannot be used to represent diagram 1.
2016-06-28 3:47 pm
這就是在於2歐姆電阻是跨接電錶或是2歐姆電阻是接於兩串接電阻間
如果是畫成圖二
可見圖一的2歐姆電阻是跨過由R,R所構成的串聯電阻直接接到電壓表並沒有與R,R串聯電阻的中間連接
這應該是圖一沒有畫得很清楚所致
如果是畫成圖二
可見圖一的2歐姆電阻是跨過由R,R所構成的串聯電阻直接接到電壓表並沒有與R,R串聯電阻的中間連接
這應該是圖一沒有畫得很清楚所致
收錄日期: 2021-04-11 21:29:42
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20160617224713AAJBabj