Problem 32

Repeat Problem 31, now assuming that each battery has an internal resistance $r = 1.4 \; \Omega$ .

Figure 19-59.

I_1 = 0.59 \textrm{ A left, } I_2 = 0.27 \textrm{ A left}

Giancoli 7th Edition, Chapter 19, Problem 32 solution video poster

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COMMENTS

By merkinthedark on Wed, 4/6/2016 - 8:02 PM

If in the previous problem we discovered that currents I1 and I2 go to the left then why is the junction rule applied so that I1= I2+I3? Is it not I3=I1+I2?

By Mr. Dychko on Thu, 4/7/2016 - 4:09 AM

Hi merkinthedark, thanks for the question. Yes, we could have used knowledge from problem 31 to choose $I_2$ to the left, and this would be fine, but we don't have to do that. There's no particular reason why I didn't. It isn't important to be correct with the initial guess about the current direction. One just has to make a choice and then construct the equations accordingly. You'll notice that the final answer in this problem has $I_2$ going to the left after all, as we expect from our work in problem 31, so we arrive at the correct answer despite using an initial guess in the other direction.

All the best,
Mr. Dychko

Repeat Problem 31, now assuming that each battery has an internal resistance r=1.4 Ωr = 1.4 \; \Omegar=1.4Ω.

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Repeat Problem 31, now assuming that each battery has an internal resistance $r = 1.4 \; \Omega$ .