# Circuit Theory Question KCL and Dependent Sources?

• Engineering

## Homework Statement

I need to find the voltages (if any) and currents of these circuit, but particularly Io
I do know that I have to use KCL bot I dont know how, can somebody help me with a node or somethinghttps://www.physicsforums.com/attachments/c2-jpg.80412/ [Broken]

I do not have any other info apart from this image

KCL

## The Attempt at a Solution

I don't know how to tackle this problem
I think by KCL

-Io = -I(Vx)+5A-3Vx

but not sure

and how do I find Vx? is
Vx=I(5 amp)*R(4 ohm)=5*4=20 volts ??????

then the dependent current is 3*20=60 volts? but is current it should be on ampere not volt

or should I solve the resistors and get Req
1/ (1/(8+4)+1/6) = 4 ohm = Req

there is one node on the top and another one on the bottom, but that one is ground, so shoul I transform the current source and the Io resistor into a voltage source?

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## Answers and Replies

Orodruin
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
Why don't you try applying KCL yourself and show us what you get. Note that providing an attempt is mandatory according to forum rules, we need to see where/if you go wrong to help you properly with your understanding.

donpacino
Gold Member

## Homework Statement

I need to find the voltages (if any) and currents of these circuit, but particularly Io
I do know that I have to use KCL bot I dont know how, can somebody help me with a node or somethinghttps://www.physicsforums.com/attachments/c2-jpg.80412/ [Broken]

I do not have any other info apart from this image

## Homework Equations

View attachment 80414
KCL

## The Attempt at a Solution

I don't know how to tackle this problem
I think by KCL

-Io = -I(Vx)+5A-3Vx

but not sure

and how do I find Vx? is
Vx=I(5 amp)*R(4 ohm)=5*4=20 volts ??????

then the dependent current is 3*20=60 volts? but is current it should be on ampere not volt

or should I solve the resistors and get Req
1/ (1/(8+4)+1/6) = 4 ohm = Req

View attachment 80414

there is one node on the top and another one on the bottom, but that one is ground, so shoul I transform the current source and the Io resistor into a voltage source?
you are on the right track

-Io = -I(Vx)+5A-3Vx There is an error in this equation.

Remember that in most cases you must have one equation for every unknown.
This implies that you might have to apply Kirchhoff's laws one more time (seeing as there are two unknowns).

Last edited by a moderator:
you are on the right track

-Io = -I(Vx)+5A-3Vx There is an error in this equation.

Remember that in most cases you must have one equation for every unknown.
This implies that you might have to apply Kirchhoff's laws one more time (seeing as there are two unknowns).

so my node is 5 (the current source) = Io (the one I need to find) + 3Vx (the one with the dependent source) + I1 (the one with the 8 and 4 resistances)

5=Io+3Vx+I1

I1=Vt/12
Vt=V(in 4)+V(in 8)
Vt=Vx+2Vx
Vt = 3 Vx

I1 = Vx/4

my unknowns are Io and Vx,

5=Io+3Vx+Vx/4

I really have no clue where is the other equation

donpacino
Gold Member
so my node is 5 (the current source) = Io (the one I need to find) + 3Vx (the one with the dependent source) + I1 (the one with the 8 and 4 resistances)

5=Io+3Vx+I1

I1=Vt/12
Vt=V(in 4)+V(in 8)
Vt=Vx+2Vx
Vt = 3 Vx

I1 = Vx/4

my unknowns are Io and Vx,

5=Io+3Vx+Vx/4

I really have no clue where is the other equation
I see 3 voltage nodes. If you reference one as ground, the other two are unknown.