Resistance/Circuit Help Badly Needed

  • Thread starter Saladsamurai
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In summary, the speaker is seeking help with finding the currents in a circuit lab using the "Ladder Method" and the "Scale Factor Method". They have already measured some currents but need to use theory to find others, specifically i_4. They believe that i_4 should be the same as the current across R_{eq}, but this is not the case according to their measurements. They are also not allowed to use Kirchoff's Law in their calculations.
  • #1
Saladsamurai
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!Resistance/Circuit Help Badly Needed!

Homework Statement



I am doing a circuit lab with the voltage and resistors shown. I have already measured the currents across each resistor, but now I need to use some of the theory that we have learned in class. Here is an image of the original circuit.

Picture1-10.png


As you can see I have reduced it to a single equivalent circuit.

Now I am working backwards to try and find the currents shown. Now keep in mind that the index for the current i may not be the same index as its respective resistor... that is, [itex]i_1[/itex] does not necessarily coincide with [itex]R_1[/itex]. I realize that that is annoying, but I did not type up the lab!

Now can someone help me to just find [itex]i_4[/itex] for now. I know that the current across [itex]R_{eq}[/itex] is 307.3 mA.

I also know that (working backwards) that [itex]R_{eq}[/itex] was made up from [itex]R_{6}+R_{12345}[/itex] which were in series with each other.

So shouldn't the current across [itex]R_{12345}[/itex] be the same as the i_total ? Thus making i_4=i_total=307.3 mA

Now I am pretty sure that I am not correct in saying this (because my measure currents dictate so) but I am not sure why?

Also, it says to find the currents sing the "Ladder Method"...I am assuming the above is just that.
I also have to find the currents using the "Scale Factor Method"... can someone clue me into how to do that one? I know it has to do with making an assumption and then calculating the currents based on it and this in turn leads to a scale factor.
 
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  • #2
Any ideas on what I am doing wrong?
 
  • #3
The way i have always done it is through Kirchoffs law.. using I1=I2+I3 then replacing the terms with ohms law V=IR and in the end getting a load nice simultanius equations, one for each loop of the circuit, in your case three.

I you don't know this method, Ill explain more if needed?

The last diagram, why have you taken out the resistor?
 
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  • #4
farso said:
The way i have always done it is through Kirchoffs law.. using I1=I2+I3 then replacing the terms with ohms law V=IR and in the end getting a load nice simultanius equations, one for each loop of the circuit, in your case three.

I am not supposed to use Kirchoff's Law.
farso said:
The last diagram, why have you taken out the resistor?

Not sure what you mean. There is clearly a resistor in the last diagram. R_eq.
 

1. What is resistance and why is it important in circuits?

Resistance is the measure of how much a material or component resists the flow of electricity. It is important in circuits because it determines the amount of current that will flow through the circuit and affects the overall performance of the circuit.

2. How do I calculate resistance in a circuit?

Resistance can be calculated using Ohm's Law, which states that resistance (R) is equal to the voltage (V) divided by the current (I). This can be represented by the equation R = V/I. Resistance can also be calculated using the color code on resistors, where each color represents a specific value.

3. What are the different types of resistors?

There are several types of resistors including fixed resistors, variable resistors, and thermistors. Fixed resistors have a set value that cannot be changed. Variable resistors, also known as potentiometers, have a resistance that can be adjusted. Thermistors are temperature-sensitive resistors that change resistance based on the temperature.

4. How do I troubleshoot a circuit with resistance issues?

If you are experiencing resistance issues in a circuit, the first step is to check all connections and make sure they are secure. You should also check for any damaged components, such as a broken resistor. Using a multimeter, you can measure the resistance at different points in the circuit to identify where the issue may be occurring.

5. How can I reduce resistance in a circuit?

There are a few ways to reduce resistance in a circuit. One way is to use thicker wires, as thinner wires have higher resistance. Another option is to use conductive materials with lower resistance, such as copper. You can also reduce resistance by adjusting the length and layout of the circuit, as longer and more complex circuits tend to have higher resistance.

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