Electronics RLC Ciruit question

Thread Starter

jeffrey1027

Joined Nov 9, 2014
5
Replace the inductor with a voltage source. Place the polarity symbols into the voltage source. Now you have two voltage soruces in series. Do you know how to "add" two voltage sources in series?
I think i figured out where the mistake I made
Vx = -VL + (-Vs)
= - ( 0 - j 43.68 V) + [- (-55 + j22 V)]
= + 55 + 21.7j V

Isn't adding voltage sources the same as adding resistors in series? Req = R1 + R2 +...+ Rn
 

shteii01

Joined Feb 19, 2010
4,644
Isn't adding voltage sources the same as adding resistors in series? Req = R1 + R2 +...+ Rn
The current enters the "resistor" from the bottom and moves up. The terminal where current enters is assumed to be positive. The terminal where current exits the "resistor" is assumed to be negative. The current flows from higher voltage potential to lower voltage potentia.

So the bottom terminal is positive, upper terminal is negative. But the voltage across the "resistor" is -43.68j volts. What does that mean? It means that our earlier assumptions about which terminal is at higher electrical potential (positive) were wrong. So we will do a simple thing. We will make upper terminal of the "resistor" positive, bottom terminal will be negative, and now instead of -43.68j volts we have +43.68j volts.

Also now we have two voltages connected from positive pole to negative pole, now we really can add two series voltages: Vx=-55+22j+43.68j
 

Thread Starter

jeffrey1027

Joined Nov 9, 2014
5
The current enters the "resistor" from the bottom and moves up. The terminal where current enters is assumed to be positive. The terminal where current exits the "resistor" is assumed to be negative. The current flows from higher voltage potential to lower voltage potentia.

So the bottom terminal is positive, upper terminal is negative. But the voltage across the "resistor" is -43.68j volts. What does that mean? It means that our earlier assumptions about which terminal is at higher electrical potential (positive) were wrong. So we will do a simple thing. We will make upper terminal of the "resistor" positive, bottom terminal will be negative, and now instead of -43.68j volts we have +43.68j volts.

Also now we have two voltages connected from positive pole to negative pole, now we really can add two series voltages: Vx=-55+22j+43.68j
Thanks a lot for the help!
 
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