Hello. I am confused with the direction of currents i1 and i3. Can anyone explain why current i1 and i3 have different directions with voltage sources? The direction of i1 should head to 60V voltage source.

 

hi Chalie,
Welcome to AAC.
Look over the video, it should help.
About 15 minutes from the start, explains a circuit similar to yours.

BTW: what do you make the i1 current value in your circuit.???

E

 

When setting up the Kirchhoff’s law equations you can point any current in either direction. The solution will then give you a negative number if it is in the opposite direction.

 

View attachment 270536Hello. I am confused with the direction of currents i1 and i3. Can anyone explain why current i1 and i3 have different directions with voltage sources? The direction of i1 should head to 60V voltage source.

Hello there,

When dealing with symbolic current indications (letters vs numbers) it is common for the variable to be completely unspecified both in value and in sign. That means if you see a current arrow and it is labeled "i7" or any other variable name it can be flowing in either direction and then the numerical result of that current will be either positive or negative. As a letter variable though, it can have any sign.

If you see a number though like "10" or "-4" then you know the current has a particular sign, but you cant tell when the current is just a variable unless you have some other information.

So what you say may be right, but you dont know that until you do a full analysis of the circuit (although it does look true for this circuit with a casual observation). So the answers you may find may be such as:
4.5 amps
-4.5 amps
etc.
(i just picked some random numerical values for those examples).

 

hi Chalie,
Welcome to AAC.
Look over the video, it should help.
About 15 minutes from the start, explains a circuit similar to yours.

BTW: what do you make the i1 current value in your circuit.???

E

Hi! I did not set the exact value of the i1. I was setting the direction of current and named it i1.