# Kirchoffs Law (again)

#### Dazedandconfused

Joined Nov 5, 2020
2
Morning all,
And apologies as I imagine this has been done to death, but I’m on my assignment for a HNC done via distance learning and I’m struggling with the attached Kirchoffs law equation. I’ve got this far, which I think is correct but I’m genuinely stuck now.
could anyone point me in the right directions for the next few steps?

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#### ericgibbs

Joined Jan 29, 2010
18,064
Last edited:

#### dl324

Joined Mar 30, 2015
15,849
could anyone point me in the right directions for the next few steps?
Don't use color coded schematics.

Ask a specific question instead of making us try to follow your logic in the equations. For starters, your loop equations would make more sense if you didn't jump around in the loop.

#### WBahn

Joined Mar 31, 2012
29,179
Morning all,
And apologies as I imagine this has been done to death, but I’m on my assignment for a HNC done via distance learning and I’m struggling with the attached Kirchoffs law equation. I’ve got this far, which I think is correct but I’m genuinely stuck now.
could anyone point me in the right directions for the next few steps?
Please explain where the '16' comes from in your second loop equation.

You really need to start tracking your units properly.

At the end you have two equations in two unknowns. Do you not know how to solve for the unknowns? If not, that's a math issue and you need to spend some quality time with some algebra texts or websites to build up those skills.

#### Dazedandconfused

Joined Nov 5, 2020
2
Please explain where the '16' comes from in your second loop equation.

You really need to start tracking your units properly.

At the end you have two equations in two unknowns. Do you not know how to solve for the unknowns? If not, that's a math issue and you need to spend some quality time with some algebra texts or websites to build up those skills.
I think, it's possibly a combo of the 'maths' and understanding the actual formula/law to be honest. I think because the course is a 'distance learning' all done over Zoom, it's quite difficult to follow if things don't quite make sense.

The 16 = V2 (8V) x R2 (2ohms)

I believe If I multiply equation 5 into equation 6 that will give me the final formula I need (barring multiplying out the denominators) but I'm not quite certain.

I1 + I2 = I3 - eq1

Loop 1 –

12-8 -V1+V2 >>> 4= V1-V2

4= 1/10I1 -2I2 eq2

Loop 2 –

16= V2+V3

16=2I2+1/7I3 eq3

16=2I2+ I1 + I2 eq4

CCT –

4=1/10 I1-2I2 eq5

16= I1+3I2 eq6

#### WBahn

Joined Mar 31, 2012
29,179
I think, it's possibly a combo of the 'maths' and understanding the actual formula/law to be honest. I think because the course is a 'distance learning' all done over Zoom, it's quite difficult to follow if things don't quite make sense.

The 16 = V2 (8V) x R2 (2ohms)

What do you get if you multiply a voltage, 8 V, by a resistance, 2 Ω?

You do not get 16. Nor do you get any kind of voltage, current, resistance, or power.

That is why I told you that you need to properly tract your units. Otherwise exactly what happened here will happen to you over and over again. Your loop equations are were all of the physics happens; everything after that is just math. If your set up equations are wrong, then all the correct math in the world won't lead to a correct answer.

If you track your units properly, then when you make mistakes like this you can spot them immediately and not waste a bunch of effort slogging through work that is only guaranteed to lead to a wrong answer.