Circuit analysis - finding current

In summary, there are two main methods for finding the current in a circuit: Ohm's Law and Kirchhoff's Current Law. Ohm's Law uses the equation I = V/R, where I is current in amps, V is voltage in volts, and R is resistance in ohms. Kirchhoff's Current Law states that the sum of currents entering a junction must equal the sum of currents leaving the junction in a circuit. The unit of measurement for current is ampere (A) and the direction of current flow does not affect circuit analysis, but it is important to consider when using Kirchhoff's Current Law.
  • #1
magnifik
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I have to solve for i(t) in the following circuit:

n1420k.png


i am wondering what the best way to approach this problem is. does the loop current method work in this case if i define all the currents to be flowing clockwise?

in other words,
>> A = [3 -1 -2; -1 4 0; -2 0 2]; % matrix A
>> b = [v1; -v2; v2]; % matrix b
x = A\b % solve for the currents

x =

[ 4/3 v1 + v2 ]
[ ]
[ 1/3 v1 ]
[ ]
[4/3 v1 + 3/2 v2]

so i(t) = (4/3)v1 + (3/2)v2
 
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  • #2


Thank you for your question. In order to solve for i(t) in this circuit, you can use the loop current method as long as you define all the currents to be flowing clockwise. This will ensure that the signs of the currents in your equations are consistent.

To solve for i(t), you can use the matrix method as shown in your example. This method involves setting up a system of equations using Kirchhoff's voltage law (KVL) and Kirchhoff's current law (KCL).

First, you can assign a variable for each of the currents in the circuit, including the loop current i(t). Then, using KVL, you can set up an equation for each loop in the circuit. For example, for the loop containing the voltage source v1, you can write the equation as:

3i(t) - i1 + 2i2 = v1

Next, you can use KCL to set up equations at each node in the circuit. For example, at the node between the two resistors, you can write the equation as:

i1 + i2 = 0

You can continue setting up equations for each loop and node in the circuit until you have a system of equations. Then, you can use the matrix method as shown in your example to solve for the currents, including i(t).

In summary, you can use the loop current method in this case as long as you define all the currents to be flowing clockwise. You can then use the matrix method to solve for the currents, including i(t). I hope this helps.


 

FAQ: Circuit analysis - finding current

How do you find the current in a circuit?

To find the current in a circuit, you can use Ohm's Law (I = V/R) or Kirchhoff's Current Law (the sum of the currents entering a junction equals the sum of the currents leaving the junction). You will need to know the voltage and resistance values in the circuit to use these methods.

What is Kirchhoff's Current Law?

Kirchhoff's Current Law states that the sum of the currents entering a junction in a circuit is equal to the sum of the currents leaving the junction. This is based on the principle of conservation of charge, where the total amount of current entering a junction must equal the total amount of current leaving the junction.

How is Ohm's Law used to find current in a circuit?

Ohm's Law is used to find the current in a circuit by using the equation I = V/R, where I is the current in amps, V is the voltage in volts, and R is the resistance in ohms. This equation can be rearranged to solve for current (I) by multiplying the voltage by the reciprocal of the resistance.

What is the unit of measurement for current?

The unit of measurement for current is ampere (A), which is a unit of electric current in the International System of Units (SI). It is defined as the amount of electric charge passing through a given point in a circuit per unit time.

How does the direction of current flow affect circuit analysis?

The direction of current flow does not affect circuit analysis because current is a scalar quantity (magnitude only) and does not have a specific direction. However, when using Kirchhoff's Current Law, it is important to consider the direction of current flow in order to correctly apply the law and determine the unknown currents in a circuit.

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