F.5 Physics Circult Diagram

由 JR8753 » 2008年10月23日 00:09:03 (p#1504594)

I don't know the answers of these four question. How to find them out ? banghead

佢係問果兩點既電位差定係果兩點電壓既差呢?

由 super666 » 2008年11月4日 22:30:32 (p#1511847)

回左第一題先．．．．ｏ個係搵電勢差
因為ｏ個度係並聯
在並聯電路中，係ｓａｍｅ　ｐ．ｄ（電勢差）
所以ｏ個題　ａｎｓ係０ｖ

第二題用相同方法，但留意依題個ｐ．ｄ唔係０ !!!
第三題搵左並聯電路中既總電阻先
之後用ｖ＝ｉｒ，搵返另外ｏ個ｒ係幾多

由 nwfb1601 » 2008年11月7日 23:49:22 (p#1513391)

Check Point 23:
C
Y: Potential = 0V as -ve terminal
Total resistance in this circult = 4 + 2 = 6
Therefore 4 Ohm resister take away 4V, remaining 2V
Therefore, pd = 2V

Check Point 24:
B
Total resistance in this circult = 4 + 2 = 6
Therefore, 4 Ohm resistor take away 4V, reminding 2V for the parallel circuit
2V divided by 3 Ohm + 1 Ohm
Therefore, 3 Ohm resistor takes away 1.5V
p.d. = 1.5V

Check Point 25:
C
As in parallel, same V
By V = IR, Current through 12 Ohm = 1/2 current through 6 Ohm = 0.2A
Resultant resistance of parallel circuit = 4 Ohm
By V = IR, 6 = 0.6 x (R + 4)
R = 6 Ohm

Check Point 26:
A
As 12V across 6 Ohm resistor and total V = 24V, 12V passes unknown resistor
By V = IR, resistance of unknown resistor = 6 Ohm
After close, in parallel, resultant resistance for parallel part = 3 Ohm
P.D. across parallel circuit = 24 x 3 / (3+6) = 8 V

由 ccicoltd » 2008年11月8日 09:19:15 (p#1513498)

super666 :回左第一題先．．．．ｏ個係搵電勢差
因為ｏ個度係並聯
在並聯電路中，係ｓａｍｅ　ｐ．ｄ（電勢差）
所以ｏ個題　ａｎｓ係０ｖ

除非兩點都喺並聯的 resistor 前面，否則好似題目咁，其中一點過阻 resistor，就點都會有 p.d.