Complex currents and voltages - current in a branch

In summary, the conversation discusses the problem of calculating |I_1| and proposes using the equation V_m = Z_{total}I_1 to solve it. The attempt involves finding Z_{total} and using it to calculate I_1. The final equation for I_1 is given as |I_1| = \frac{|V_m(1 - w^2LC + jwCR)|}{\sqrt{R^2 + (wL)^2}}. The speaker expresses doubts about the given answer, which does not include the capacitor impedance, and asks for help.
  • #1
Rectifier
Gold Member
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The problem
I want to calculate ## |I_1| ##

RCMQMNp.jpg


The attempt

## V_m = Z_{total}I_1 \\ I_1 = \frac{V_m}{Z_{total}} ##

## Z_{total} = \frac{ \frac{1}{jwC }\cdot (R + jwL) }{\frac{1}{jwC} + R + jwL} \\ \frac{ R + jwL }{1 + jwCR + jwCjwL} \\ \frac{ R + jwL }{1 - w^2LC + jwCR } \\ ##

## I_1 = \frac{V_m}{Z_{total}} = \frac{V_m}{\frac{ R + jwL }{1 - w^2LC + jwCR }} \\ = \frac{V_m(1 - w^2LC + jwCR)}{R + jwL} ##

## I_1 = \frac{V_m(1 - w^2LC + jwCR)}{R + jwL} \\ |I_1| = \frac{|V_m(1 - w^2LC + jwCR)|}{\sqrt{R^2 + (wL)^2}} ##

This does not look right since the answer is ## \frac{R|V_m|}{R^2 + (wL)^2} ##

Please help me.
 
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  • #2
The given answer looks very suspicious since it doesn't include the capacitor impedance in any way. Your result looks okay to me.
 

Related to Complex currents and voltages - current in a branch

1. What is a complex current and voltage?

A complex current and voltage refers to the combination of both real and imaginary components in an alternating current (AC) circuit. In AC circuits, the current and voltage values are constantly changing in a sinusoidal pattern, and the presence of imaginary components accounts for the phase difference between current and voltage.

2. How is complex current measured?

Complex current is measured using a device called an oscilloscope, which displays both the magnitude and phase of the current. The magnitude is measured in units of amperes (A), while the phase is measured in units of degrees.

3. What is the difference between current in a branch and total current?

The total current in a circuit is the sum of all the individual branch currents, whereas the current in a branch is the amount of current flowing through a specific branch of the circuit. This is important to understand when analyzing complex circuits with multiple branches.

4. How does current behave in a series circuit?

In a series circuit, the current remains constant at all points in the circuit. This means that the current in one branch of the circuit is the same as the current in any other branch.

5. How does current behave in a parallel circuit?

In a parallel circuit, the total current is divided between the branches based on their individual resistances. The branch with the least resistance will have the highest current, while the branch with the highest resistance will have the lowest current.

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