# Current in multi-loop circuit

1. May 13, 2007

### mbrmbrg

1. the problem
In Figure 27-69 (see attached), the ideal each resistance is 4.50 and V1 = 11.0 V.

(a) What is the size and direction of current i1? (Take upward to be positive.)
(No Response)[-2.44] A
(b) What is the size and direction of current i2? (Take upward to be positive.)
(No Response)[-1.33] A
(c) At what rate is energy being transferred at the 4.00 V battery and is the battery supplying or absorbing energy?
(No Response)[5.33] W (No Response)[ supplying ]
(d) At what rate is energy being transferred at the 11.0 V battery and is the battery supplying or absorbing energy?
(No Response)[41.6] W (No Response)[ supplying ]

Attempted Solution

Help needed with part b.

for part a: we ignored the right hand part of the cirucuit, and just did the left-most loop. Then we summed the voltages and set them to zero, and got the correct answer.

for part b: We looked at the two right loops and combined them by saying that there are two resistors in parallel which can be replaced by $$R_{eq}=\frac{1}{R}+\frac{1}{R})^{-1}$$. Then we tried ignoring the left loop and summing the voltages in the middle loop (with the top right resistor replaced by R_eq) and setting everything equal to zero. That's the wrong answer.
Frankly, I don't understand why $$i_2\neq i_1$$.
And the bloody final is tomorrow

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2. May 13, 2007

### mbrmbrg

Here's a better diagram, I think, which hopefully will be approved a little more quickly.

In the new diagram, the two resistors being combined are R3 and R4.

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