Circuit with 2 loops, find the current in one of the loops

AI Thread Summary
The discussion focuses on calculating the current I1 through resistor R1 in a circuit with a battery and four resistors. The user initially calculates the total current as 2.47A by summing resistances in series and applying the parallel resistance rule. However, they suspect an error in determining the current in the first loop, where they incorrectly multiplied the total current by a ratio of resistances. Another participant suggests simplifying the approach by directly using the voltage across a resistor to find the current with I = V/R. The key takeaway is to ensure proper application of voltage and resistance values to accurately determine current in circuit loops.
jenzao
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Homework Statement


A circuit composed of one battery and four resistors is arranged as shown in the attached pic.

E = 19 V

R1 = 12 W
R2 = 2 W
R3 = 15 W
R4 = 2 W


Calculate the current I1 through R1?




Homework Equations


V=IR (obviously)



The Attempt at a Solution



first i got the net current in this circuit by doing the following..
i summed resistors in series to get 14ohm on first loop and 17ohm on second loop.
then i applied resistance in parallel rule :
Req = (1/R1) + (1/R2)
= 7.69ohm = Rtotal
then I = V/R = 2.47A = total current in the circuit.

Then to get the current on the 14 ohm loopm i multiplied 2.47 by (14/17) . ( i think this is where I am erring, but can't see why this doesn't work??)

= 2.03A (wrong)
thanks for any help!

 

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you're making this too complicated.

the voltage between the two nodes must be the battery voltage.

so if you know the voltage across a resistor (or an Eq Res) you can find the current through it.


use I = V/R, where R is the equivalent resistance of the branch and V is the voltage across the branch.
 
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