Hi guys,

May I know to find the current IS3 why are able to use KCL because there are 3 voltage sources (20v, 5v,8v) in this circuit how is the current distribution? normally using KCL only have one current source

 

Hi Alex,
Is this question a Homework or College assignment?
Moderation.

 

Hi Alex,
Is this question a Homework or College assignment?
Moderation.

personal study

 

The steps in the calculation of Is3 are all set out above, but not in the clearest fashion.

 

The steps in the calculation of Is3 are all set out above, but not in the clearest fashion.

able to explain to me why able to use KCL

 

Why Gustav was given credit for making Georg's elegantly simple law more complicated has always been a mystery to me.

Use Ohm's law. Va = 20 volts. Vb = 20 - 5 = 15 volts, Vc = 8 Volts.
So I1 = (Va-Vc)/R1 = (20-8)/10 = 1.2A and I2 = (Vb - Vc)/R2 = (15-8)/4 = 1.75A
Since the arrow for IS3 is drawn pointing the wrong way the current is the negative sum of 1.2 and 1.75 = -2.95

If you are being taught to do unrealistic problems using Kirchoff's laws I'd recommend looking for a better course. I've interviewed so many new graduate engineers who can do this kind of problem but have no idea how to address real world problems.

 

able to explain to me why able to use KCL

KCL can be applied at any circuit node. In this case the node labelled Vc is the one being considered.

 

Why Gustav was given credit for making Georg's elegantly simple law more complicated has always been a mystery to me.

Use Ohm's law. Va = 20 volts. Vb = 20 - 5 = 15 volts, Vc = 8 Volts.
So I1 = (Va-Vc)/R1 = (20-8)/10 = 1.2A and I2 = (Vb - Vc)/R2 = (15-8)/4 = 1.75A
Since the arrow for IS3 is drawn pointing the wrong way the current is the negative sum of 1.2 and 1.75 = -2.95

If you are being taught to do unrealistic problems using Kirchoff's laws I'd recommend looking for a better course. I've interviewed so many new graduate engineers who can do this kind of problem but have no idea how to address real world problems.

may I know there are 3 voltage sources how is the KCL able to apply ?

 

Why do you think the number of voltage sources is important? KCL doesn't care.

 

Use Ohm's law.

Why do you think the number of voltage sources is important? KCL doesn't care.

why are these cases able to apply KCL based on nodes?

 

why are these cases able to apply KCL based on nodes?

Alex, you may not have understood my point. KCL is, in my view, not worth your time. Honestly, since I've never seen the point of KCL, at least in real world problems, I'm not the best person to give you a sensible answer. Why do you care? The circuit in your post is completely artificial, which is why I recommended finding a better course which teaches and tests real world problems.

 

why are these cases able to apply KCL based on nodes?

Because "Kirchhoff's Current Law, often shortened to KCL, states that “The algebraic sum of all currents entering and exiting a node must equal zero.”

 

Alex, you may not have understood my point. KCL is, in my view, not worth your time. Honestly, since I've never seen the point of KCL, at least in real world problems, I'm not the best person to give you a sensible answer. Why do you care? The circuit in your post is completely artificial, which is why I recommended finding a better course which teaches and tests real world problems.

Hi Jerry-Hat-Trick
Any recommendation course that teaches real-world project