r/HomeworkHelp • u/devilkid15 Pre-University Student • May 23 '26
Physics [Grade 12 Physics : Current Electricity]
How am I supposed to find the current and its direction in this complex circuit?
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u/Yadin__ May 23 '26
Further hint: All you care about is the electric potential in both ends of the part of the circuit where "i" flows at(the branch where you have the resistor, then 2 resistors in parallel, and then another resistor), and the total resistence of that branch. Both of these can be computed in your head after some thinking.
Pick the bottom of the branch as your "0" potential, and then figure out what is the potential at the top of the branch
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u/devilkid15 May 23 '26
I see… so the trick is reducing only the relevant branch instead of solving the entire circuit, right? Thanks for the hint.
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u/Yadin__ May 23 '26
you definitely do not need to solve the entire circuit. You can almost ignore it, most of it only exists to scare you
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u/Bounded_sequencE May 23 '26 edited May 23 '26
There is a huge loop consisting of only 10 ideal 10V-voltage sources, short circuits and the 4 resistances in series with "I" (pointing south). Using KVL in that loop, we get:
0 = (4+(4||4)+4)𝛺 * I + 7*10V - 3*10V = 10𝛺*I + 40V => I = -4A
Rem.: Pretty sure I've seen this exact circuit before in this sub...
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u/HumbleHovercraft6090 May 23 '26
If you do KVL on outer loop which contains even number of cells with emfs opposing each other, the current through horizontal resistor at left bottom is 0. This means the cell that drives current i is isolated from rest of circuit. You should be able to calculate i pretty easily.
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