Resistance/Circuit Help Badly Needed

  • Thread starter Thread starter Saladsamurai
  • Start date Start date
AI Thread Summary
The discussion revolves around a circuit lab where the user seeks help in calculating the current i_4 based on measured values and theoretical methods. The user has determined that the equivalent resistance, R_eq, consists of resistors R_6 and R_{12345} in series, leading to confusion about the current distribution. They question whether the current across R_{12345} should equal the total current of 307.3 mA, despite measured currents suggesting otherwise. The user also seeks clarification on the "Ladder Method" and "Scale Factor Method" for calculating currents, expressing a preference for using Kirchhoff's Law, which they are advised not to use. The discussion highlights the challenges of applying different circuit analysis methods while trying to reconcile theoretical concepts with practical measurements.
Saladsamurai
Messages
3,009
Reaction score
7
!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, i_1 does not necessarily coincide with R_1. I realize that that is annoying, but I did not type up the lab!

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

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

So shouldn't the current across R_{12345} 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.
 
Last edited:
Physics news on Phys.org
Any ideas on what I am doing wrong?
 
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?
 
Last edited:
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.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Back
Top