Finding Current Through Resistors in Figure

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In summary, the problem involved determining the magnitude of the current through all the resistors shown in the figure, with batteries of E1 = 9.00V and E2 = 12.00V and resistors of R1 = 15.8Ohm, R2 = 22.3Ohm, and R3 = 34.3Ohm. The conversation discusses setting up equations and using substitutions to solve for the current values, with the final values being I1 = 0.1986 A, I2 = 0.515 A, and I3 = 0.3164 A. However, corrections were made to the equations and the correct values were determined to be I1 = 0
  • #1
khoaz
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Determine the magnitude of the current through all the resistors shown in the figure

The batteries have emfs of E1 = 9.00V and E2 = 12.00V and the resistors have values of R1 = 15.8Ohm , R2 = 22.3Ohm, and R3 = 34.3Ohm.maybe I am just setting up my equations wrong?
E2 - I3R3 - I2R2 = 0
E1 - I1R1 - I2R2 = 0
I2 = I1 + I3

so i used one equation to solve for the other unknowns, and plugged in the i2 = i1 + i3 equation in the beginning. than used that equation to solve for the final one. maybe my algebra got screwed up along the way or something. it takes like a page working through the problem only to see that you didnt get it.so solving for I1 i tried
E2 -I1R1 - R2(E2 + I1R3)/(R3 + R2) = 0
which turned out to be .515 AI2:
E2 - R3(I2 + [I2R2/R1]) - I2R2 = 0
which turned out to be .199 AI3:
E1 - I3R3 - I3R2 - R2(E2 - I3R2)/(R1 + R2) = 0
which turned out to be .2299 A
sadly they're all wrong.
 

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  • #2
E2 - I3R3 - I2R2 = 0
E1 - I1R1 - I2R2 = 0
I2 = I1 + I3
are correct. One must be careful with the substitutions and signs.

E2 - I3R3 - I2R2 = 0
E1 - I1R1 - I2R2 = 0

and one can use I2 = I1 + I3 to change I3 into I2 - I1.

With E2 - (I2 - I1) R3 - I2 R2 = 0
and E1 - I1 R1 - I2 R2 = 0,

one has two equations and two unknowns I1 and I2, and then find I3.
 
  • #3


I would first check my calculations to ensure that I have used the correct equations and values for the resistors and emfs. I would also double check my algebra to make sure there are no errors. Additionally, I would consider the direction of the current flow and whether it aligns with the assumed direction in the equations. If all of these factors check out, then I would suggest using a circuit simulator or conducting an actual experiment to verify the values of the current through each resistor. It is possible that there may be additional factors at play, such as internal resistance of the batteries or temperature effects, that may affect the final values. It is important to thoroughly analyze and troubleshoot any discrepancies in order to ensure accurate results.
 

1. How do I calculate the current through a resistor in a circuit?

To calculate the current through a resistor, you can use Ohm's Law (I=V/R) where I is the current in amps, V is the voltage across the resistor in volts, and R is the resistance in ohms.

2. What is the relationship between current, voltage, and resistance in a circuit?

Current, voltage, and resistance are all related through Ohm's Law. As the resistance increases, the current decreases, and as the voltage increases, the current also increases.

3. Can I use a multimeter to measure current through a resistor in a circuit?

Yes, a multimeter can be used to measure the current through a resistor by setting it to the appropriate current range and placing the probes in series with the resistor.

4. How does the placement of a resistor in a circuit affect the current?

The placement of a resistor in a circuit can affect the current by either increasing or decreasing it, depending on its value and the voltage across it. A higher resistance will decrease the current, while a lower resistance will increase the current.

5. What is the difference between series and parallel circuits in terms of current through resistors?

In a series circuit, the current through each resistor is the same, while in a parallel circuit, the current is divided among the resistors. This is due to the different paths the current can take in a parallel circuit, resulting in a different overall resistance and current flow.

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