How to treat internal resistance in calculations ?

[Femme_physics]

Not sure what you mean.
What do you have in mind?

My bad. I forgot Kirchhoff law is applied only to a single closed loop. But why did we necessarily choose the right divergence to the 10V source? Would picking the left side divergence of the closed loop using the 10V source legit as well? (the loop marked in red)
http://img6.imageshack.us/img6/7064/isitokay.jpg

That's an awkward way to learn!
Can't look ahead and forces you to do things exactly in the pace the teacher sets.

Same way in materials science. We cope with what we get, and try to solve exercises often a bit our of our league. :-/

 

[I like Serena]

My bad. I forgot Kirchhoff law is applied only to a single closed loop. But why did we necessarily choose the right divergence to the 10V source? Would picking the left side divergence of the closed loop using the 10V source legit as well? (the loop marked in red)

Random choice.
But yes, you can also choose your red loop. :)

Same way in materials science. We cope with what we get, and try to solve exercises often a bit our of our league. :-/

Then it's good that you already know a bit more about electronics!
If you get an exercise now, it won't be out of your league, but it'll be easy peasy! :)

 

[Femme_physics]

Random choice.
But yes, you can also choose your red loop. :)

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NOW it's clear :) I feel so empowered to do math and electronics now! You wanted me to find I₂ though? Well, I have 3 equations with 3 unknowns, I just plug the result of I₁ to the equations to get what I need.

#1
-60 x 0.2 -20I_L+18 = 0
I_L = 0.3 [A]


Plugging that to the last equation:
I₁+I₂-I_L=0
0.2+I₂-0.3=0
I₂=0.1 [A]
There!

 

[I like Serena]

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:rofl:

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NOW it's clear :) I feel so empowered to do math and electronics now! You wanted me to find I₂ though? Well, I have 3 equations with 3 unknowns, I just plug the result of I₁ to the equations to get what I need.

Oh yeah, I'd completely forgotten about that! :)

#1
-60 x 0.2 -20I_L+18 = 0
I_L = 0.3 [A]


Plugging that to the last equation:
I₁+I₂-I_L=0
0.2+I₂-0.3=0
I₂=0.1 [A]
There!

Very good!

However, I'm afraid I miss remembered. I thought I₂ would come out negative, meaning that the 10 V battery would be charging.
Anyway, I think that point is kind of moot now.

 

[Femme_physics]

Anyway, I think that point is kind of moot now.

It'd probably come up in other problems :)

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:D This is by far the longest homework help thread I ever had! Much obliged, ILS, gneill. You rock^^

Never thought I'd pass the 70 replies!

 

[I like Serena]

This is by far the longest homework help thread I ever had! Much obliged, ILS, gneill. You rock^^

Never thought I'd pass the 70 replies!

Apparently you were given a problem that you wouldn't be able to solve with the knowledge they imparted on you.

And not only did you solve the problem anyway, but you learned an entire new field of science to handle all of these problems!
I'm sorry it took us over 70 posts to teach you this entire field. :P

I suspect you will be the only one in your class that will have solved this problem, unless another student has an unfair advantage.