Originally Posted by **allim** The following questions were taken from a quiz held earlier this year. An answer sheet has been provided, but I 'm a little confused as to how and why the answers are correct.
1. What is the effective resistance between the points P and Q? (Refer to the attachment.) Ans: 3 Ohms
Any help would be greatly appreciated. |

Let me tell you for the first problem. Consider the leftmost two 3 ohm resistors, they are actually in series. Group them together and you got 6 ohm. This equivalent resistance is actually in parallel with the 6 ohm resistor. Then 1/(3+3) + 1/6 = 1/R where R is the new equivalnet resistance. As the process continues, you would get you answer

For question 3, again group all the resistors. Consider the 3 resistors on the right. Let R' be the equivalent resistance.1/R'= 1/R + 1/2R

R'=2R/3

then let new equivalent resistance be R''

1/R''=1/R + 1/(2R/3)

R''=2R/5

ler final equivalent resistance be R'''

R'''=2R/5+R = 7R/5

P = V^2/R'''

58 = (45)^2/(7R/5)

R=25 ohm

I guess the answer of mine is correct instead of 24 ohm