(series)
E (20V) >>> R1(20kohm) >>> R2(???kohm) >>> R3(40kohm) >>>
用 Vmeter 包圍 R3 有 8V.
點搵 R2 的電阻值?
請問點搵呢個 R2 電阻值???
2009-09-30 5:59 pm
回答 (2)
2009-09-30 11:05 pm
✔ 最佳答案
因為電路係 in Series, 所以 current 經過每個電阻都會一樣.I = V / (R1 + R2 + R3)
I = V3 / R3
所以:
V / (R1 + R2 + R3) = V3 / R3
20 / (20k + R2 + 40k) = 8 / 40k
20 x 40k = 8 x (60k + R2)
800k = 480k + 8 x R2
R2 = (800k -480k) / 8
R2 = 40kohm
checking:
20 / (20k + 40k + 40k) = 8 / 40k
20 / 100k = 8 / 40k = 0.2mA
2009-10-01 6:49 am
因申聯, 先計R3的電流先 I3 = V3/R3 = 8V / 40k = 0.2mA, 因串聯, I1=I2=I3 = 0.2mA. 計算V1= I1 xR1 = 0.2mA x 20k = 4V.
計算V2 = E -- V1 -- V3 = 20V -- 4V -- 8V = 8V
計算R2 = V2 / I2 = 8V / 0.2mA = 40k
計算V2 = E -- V1 -- V3 = 20V -- 4V -- 8V = 8V
計算R2 = V2 / I2 = 8V / 0.2mA = 40k
收錄日期: 2021-04-23 18:22:08
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20090930000051KK00281