Kirchhoff's Laws: Homework Solutions Check

[frazdaz]

Homework Statement

Homework Equations

$$\sum I_{in} = \sum I_{out}$$
$$\sum \epsilon = \sum pd$$

The Attempt at a Solution

Can anyone identify any mistakes in these? Probably signs

$$I = I_1 + I_2$$
$$12=4I_1 +3I$$
$$5=4I_1 - 2I_2$$
$$12-5=2I_2+3I$$

 

[BvU]

What let's you think there are any mistakes ?

 

[frazdaz]

What let's you think there are any mistakes ?

The answers have I₁ and I₂ with opposite signs. I get them both as positive.

 

[NascentOxygen]

I make all currents positive for the directions shown.

I'm not sure what is achieved by that + sign accompanying each current arrow? It seems superfluous if it duplicates the function of the arrowhead, and just clutters the diagram.

 

[frazdaz]

I make all currents positive for the directions shown.

I'm not sure what is achieved by that + sign accompanying each current arrow? It seems superfluous if it duplicates the function of the arrowhead, and just clutters the diagram.

Well that's good news. And, yeah, I guess it's just intended to help with the maths side of things.