Finding current in a circuit using Kirchhoff voltage law

In summary, the conversation discusses the application of Kirchhoff's voltage law to a circuit and the attempt at solving for the current. The ammeter reads 2 A and by using the equation 0 = -18V + (7 ohms)(I1) + (5 ohms)(2 A) + 3V, the current I1 is found to be -0.714 A. However, the solution does not have a negative sign and it is suggested that there may have been an algebra mistake in the equation.
  • #1
wanderer0102
1
0

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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  • #2
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 :\
 

1. How do you use Kirchhoff's voltage law to find the current in a circuit?

Kirchhoff's voltage law states that the sum of the voltages around a closed loop in a circuit must equal zero. To find the current in a circuit using this law, you need to first identify all the voltage sources and resistors in the circuit. Then, you can use the equation V = IR to calculate the voltage drop across each resistor. Finally, you can use Kirchhoff's voltage law to set up and solve equations to find the unknown currents in the circuit.

2. Can Kirchhoff's voltage law be applied to any type of circuit?

Yes, Kirchhoff's voltage law can be applied to any type of circuit, whether it is a simple series or parallel circuit, or a more complex circuit with multiple loops. This law is a fundamental principle in circuit analysis and is applicable to all types of circuits.

3. What is the difference between Kirchhoff's voltage law and Ohm's law?

Kirchhoff's voltage law is used to analyze circuits and calculate the voltages and currents within them, while Ohm's law is used to relate the voltage, current, and resistance of a single resistor. Kirchhoff's voltage law takes into account the sum of all voltages in a closed loop, while Ohm's law only considers the voltage and current across a single resistor.

4. Are there any limitations to using Kirchhoff's voltage law?

Kirchhoff's voltage law is based on the principle of conservation of energy and is a valid method for solving circuits. However, it does have some limitations, such as assuming ideal conditions in the circuit and not taking into account the inductance and capacitance of components. In certain cases, other methods such as nodal analysis may be more appropriate.

5. Can Kirchhoff's voltage law be used to find the voltage at a specific point in a circuit?

Yes, Kirchhoff's voltage law can be used to find the voltage at a specific point in a circuit. By setting up equations with the known voltages and resistances in the circuit and using Kirchhoff's voltage law, you can solve for the voltage at the desired point. However, this method may become more complex in circuits with multiple loops or non-linear components.

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