Finding current in a circuit using Kirchhoff voltage law

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SUMMARY

The discussion centers on applying Kirchhoff's Voltage Law (KVL) to solve a circuit problem. The user calculated the current I1 in a circuit with a voltage of -18V, resistances of 7 ohms and 5 ohms, and an ammeter reading of 2 A. The user arrived at a value of -0.714 A for I1, while the expected solution presented a positive value of +5/7 A. The discrepancy is attributed to an algebraic mistake, highlighting the importance of correctly interpreting circuit components and signs in KVL equations.

PREREQUISITES
  • Understanding of Kirchhoff's Voltage Law (KVL)
  • Basic circuit analysis techniques
  • Familiarity with Ohm's Law
  • Ability to manipulate algebraic equations
NEXT STEPS
  • Review Kirchhoff's Voltage Law applications in circuit analysis
  • Practice solving circuit problems using KVL with various configurations
  • Learn about the significance of sign conventions in circuit analysis
  • Explore common algebraic mistakes in electrical engineering calculations
USEFUL FOR

Students studying electrical engineering, educators teaching circuit analysis, and anyone seeking to improve their understanding of Kirchhoff's laws and circuit calculations.

wanderer0102
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Homework Statement


Hi, I'm learning about Kirchhoff's laws, and have to solve the circuit. Attached picture of part the circuit I am attempting to solve. The ammeter reads 2 A.

Homework Equations


Kirchhoff's voltage law says the total voltage around a closed loop must be zero.

The Attempt at a Solution


By going around the loop I get 0 = -18V + (7 ohms)(I1) + (5 ohms)(2 A) + 3V.
Then solving for the current I1 I find that it is -0.714 A. But in the solution it does not have a negative sign. What did I do wrong?
 

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wanderer0102 said:
0 = -18V + (7 ohms)(I1) + (5 ohms)(2 A) + 3V.
...
But in the solution it does not have a negative sign. What did I do wrong?
Algebra mistake? Your equation gives a positive value, +5/7

But you did not even post the full circuit :\
 

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