Circuit problem, prob really easy, please check

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Homework Help Overview

The discussion revolves around a circuit problem where the original poster seeks to find missing values in a given circuit, specifically focusing on the total resistance. The subject area pertains to electrical circuits, particularly the application of Ohm's Law and Kirchhoff's Laws.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to calculate the total resistance using Ohm's Law and questions the validity of their result. Some participants inquire about the configuration of the resistors, specifically whether they are all in parallel.

Discussion Status

The discussion is ongoing, with some participants confirming the total resistance value while clarifying that the resistors are not all in parallel. Guidance has been offered regarding the use of Kirchhoff's Laws and Thevenin's Theorem, although the original poster has not yet covered Thevenin's Theorem in their studies.

Contextual Notes

The original poster indicates a lack of familiarity with Thevenin's Theorem, which may limit their ability to fully engage with the suggested approaches.

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1. Find the missing values for the given circuit.



2. the given circuit is attached..
View attachment phys.bmp



3. soo, so far, i used ohms laws to get the total resistance, Rt = 1.4 ohms. can someone please tell me if this is right?
 
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are all of them in parallel here ?
 
The resistance of the whole circuit is indeed 1.4 ohm. The resistances are NOT all in parallel.
In general The resistance of every network of resistances can be computed by using kirchhofss laws and ohms law to get simultaneous equations for all the currents in the circuit.
You can use kirchhofs law for every 3 or more wire connection
I_1 = I_3 + i_4 for example
and ohms law and the fact that the sum of all voltages differences in a closed loop
is 0
V = R_1*I_1 + R_4*I_4
V = R_1*I_1 + R_3*I_3+R_5*I_5
etc.
(use always the same direction for I_3)
If you use enough of those you can get 5 simultaneous equations for I_1 ... I_5

There's a faster way, if you've covered Thevenins Theorem.

http://en.wikipedia.org/wiki/Thévenin's_theorem

draw another 14V voltage source to the right of R2 and R5 and parallel to the first voltage source. This won't change any currents through the resistances.
Then cut the wire between the tops of R1 and R2. Both sides of the cut will be at the same voltage before and after, so that won't change any currents either.
Then replace the left voltage source, R1 and R4 with their thevenin equivalent and do the
same with the voltage source on the right, R2 and R5.
What remains is a simple series circuit.
 
thank youu.
we haven't covered thevenin yet but wat u said made sense =)
 

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