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# More Electronics Help! Kirchhoff's law!

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Posted · Original PosterOP

Im at the end of a college assignment, and im working on Kirchhoff's law.  Ive ended up at a simultaneous equation and im stuck on what to do next. The last time i worked with algebra was when i left school ( 5 years ago)

Would anyone be able to point me in the right direction and help me?

Sorry for the bad hand writing.

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I hated that friggin law. If this hasn't been answered by the time I get home I'll help you out as best I can.

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Oh dear... this gives me some pretty traumatizing flashbacks

Either way you're almost there:

10 = 28I1 + 9I2

15 = 9I1 + 16I2

9l2 = 10 - 28I1

9l1 = 15 - 16l2

I2 = 10/9 - 28I1/9

I1 = 15/9 - 16I2/9

Now I substitute I2 in the second equation with the first equation:

I1 = 15/9 - 160/81 + 16*28I1/81 = -25/81 + 448I1/81

From here I can work out the value of I1:

367I1/81 = 25/81

367I1 = 25

I1 = 25/367 ~= 0.07

Using this result I can find the value of I2 as well by using the first equation:

I2 = 10/9 - 28(0.07)/9

I2 = (10 - 28 * 0.07) / 9 ~= 0.9

From here, I3 is just:

I3 = I1 + I2 ~= 0.97

And there you go. CHECK MY CALCULATIONS, I am merely human and I can press the wrong buttons on the calculator - but it should be correct.

-EDIT-

it was not correct. I fixed it

<Make me a sandwich.> <No! Make it yourself!> <Sudo make me a sandwich.> <FINE.> What is scaling and how does it work? Asus PB287Q unboxing! Console alternatives :D  CoC F.A.Q Beginner's Guide To LTT (by iamdarkyoshi)

Sauron'stm Product Scores:

Spoiler

Just a list of my personal scores for some products, in no particular order, with brief comments. I just got the idea to do them so they aren't many for now

Don't take these as complete reviews or final truths - they are just my personal impressions on products I may or may not have used, summed up in a couple of sentences and a rough score. All scores take into account the unit's price and time of release, heavily so, therefore don't expect absolute performance to be reflected here.

-Lenovo Thinkpad X220 - [8/10]

Spoiler

A durable and reliable machine that is relatively lightweight, has all the hardware it needs to never feel sluggish and has a great IPS matte screen. Downsides are mostly due to its age, most notably the screen resolution of 1366x768 and usb 2.0 ports.

-Apple Macbook (2015) - [Garbage -/10]

Spoiler

From my perspective, this product has no redeeming factors given its price and the competition. It is underpowered, overpriced, impractical due to its single port and is made redundant even by Apple's own iPad pro line.

-OnePlus X - [7/10]

Spoiler

A good phone for the price. It does everything I (and most people) need without being sluggish and has no particularly bad flaws. The lack of recent software updates and relatively barebones feature kit (most notably the lack of 5GHz wifi, biometric sensors and backlight for the capacitive buttons) prevent it from being exceptional.

-Microsoft Surface Book 2 - [Garbage - -/10]

Spoiler

Overpriced and rushed, offers nothing notable compared to the competition, doesn't come with an adequate charger despite the premium price. Worse than the Macbook for not even offering the small plus sides of having macOS. Buy a Razer Blade if you want high performance in a (relatively) light package.

-Intel Core i7 2600/k - [9/10]

Spoiler

Quite possibly Intel's best product launch ever. It had all the bleeding edge features of the time, it came with a very significant performance improvement over its predecessor and it had a soldered heatspreader, allowing for efficient cooling and great overclocking. Even the "locked" version could be overclocked through the multiplier within (quite reasonable) limits.

-Apple iPad Pro - [5/10]

Spoiler

A pretty good product, sunk by its price (plus the extra cost of the physical keyboard and the pencil). Buy it if you don't mind the Apple tax and are looking for a very light office machine with an excellent digitizer. Particularly good for rich students. Bad for cheap tinkerers like myself.

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28 minutes ago, Sauron said:

And there you go. CHECK MY CALCULATIONS, I am merely human and I can press the wrong buttons on the calculator - but it should be correct.

Your reply came up while I was working it out myself. But we have different answers.

I rewrote I1 as A and I2 as B, so I wouldn't mix them up.

I got I1 = 25/367 and I2 = 330/367

I checked it using an online tool to be sure and I seem to be right.

Also I wouldn't have thought that I1/2 could be negative? I remember the Simultaneous Equations a lot better than Kirchhoff's law, probably because we got the formulas on a sheet in physics!

Gaming Rig:CPU: Xeon E3-1230 v2¦RAM: 16GB DDR3 Balistix 1600Mhz¦MB: MSI Z77A-G43¦HDD: 2x240GB SSD 1.5TB+1TB HDD¦GPU: AMD R9 290 (Arctic Cooler)¦PSU: OCZ 650W¦Case: Carbide 300R

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6 minutes ago, Madgemade said:

Your reply came up while I was working it out myself. But we have different answers.

There you go, I did it in a bit of a rush your answer is probably correct.

6 minutes ago, Madgemade said:

Also I wouldn't have thought that I1/2 could be negative? I remember the Simultaneous Equations a lot better than Kirchhoff's law, probably because we got the formulas on a sheet in physics!

Current can absolutely be negative, it just means it runs in the opposite direction to the frame of reference.

<Make me a sandwich.> <No! Make it yourself!> <Sudo make me a sandwich.> <FINE.> What is scaling and how does it work? Asus PB287Q unboxing! Console alternatives :D  CoC F.A.Q Beginner's Guide To LTT (by iamdarkyoshi)

Sauron'stm Product Scores:

Spoiler

Just a list of my personal scores for some products, in no particular order, with brief comments. I just got the idea to do them so they aren't many for now

Don't take these as complete reviews or final truths - they are just my personal impressions on products I may or may not have used, summed up in a couple of sentences and a rough score. All scores take into account the unit's price and time of release, heavily so, therefore don't expect absolute performance to be reflected here.

-Lenovo Thinkpad X220 - [8/10]

Spoiler

A durable and reliable machine that is relatively lightweight, has all the hardware it needs to never feel sluggish and has a great IPS matte screen. Downsides are mostly due to its age, most notably the screen resolution of 1366x768 and usb 2.0 ports.

-Apple Macbook (2015) - [Garbage -/10]

Spoiler

From my perspective, this product has no redeeming factors given its price and the competition. It is underpowered, overpriced, impractical due to its single port and is made redundant even by Apple's own iPad pro line.

-OnePlus X - [7/10]

Spoiler

A good phone for the price. It does everything I (and most people) need without being sluggish and has no particularly bad flaws. The lack of recent software updates and relatively barebones feature kit (most notably the lack of 5GHz wifi, biometric sensors and backlight for the capacitive buttons) prevent it from being exceptional.

-Microsoft Surface Book 2 - [Garbage - -/10]

Spoiler

Overpriced and rushed, offers nothing notable compared to the competition, doesn't come with an adequate charger despite the premium price. Worse than the Macbook for not even offering the small plus sides of having macOS. Buy a Razer Blade if you want high performance in a (relatively) light package.

-Intel Core i7 2600/k - [9/10]

Spoiler

Quite possibly Intel's best product launch ever. It had all the bleeding edge features of the time, it came with a very significant performance improvement over its predecessor and it had a soldered heatspreader, allowing for efficient cooling and great overclocking. Even the "locked" version could be overclocked through the multiplier within (quite reasonable) limits.

-Apple iPad Pro - [5/10]

Spoiler

A pretty good product, sunk by its price (plus the extra cost of the physical keyboard and the pencil). Buy it if you don't mind the Apple tax and are looking for a very light office machine with an excellent digitizer. Particularly good for rich students. Bad for cheap tinkerers like myself.

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20 minutes ago, Sauron said:

Current can absolutely be negative, it just means it runs in the opposite direction to the frame of reference.

Ahh, because of the resisters I was think of resistance and I don't think you can have negative resistance resister. Negative current yes, I is current so yeah should have realised that one. Hopefully OP sees how to do the simulations equations, in math class they were much harder than that, often with indices or quadratics...

Gaming Rig:CPU: Xeon E3-1230 v2¦RAM: 16GB DDR3 Balistix 1600Mhz¦MB: MSI Z77A-G43¦HDD: 2x240GB SSD 1.5TB+1TB HDD¦GPU: AMD R9 290 (Arctic Cooler)¦PSU: OCZ 650W¦Case: Carbide 300R

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Posted · Original PosterOP
24 minutes ago, Madgemade said:

Ahh, because of the resis﻿ters I wa﻿s think of res﻿istance and I don't think you can have﻿ negativ﻿e resistance resister. Negative c﻿urrent yes, I is current so yeah should have realised that one. Hopefully OP sees how to do the simulations eq﻿uation﻿s, in math class they we﻿re much harder ﻿than that, often with i﻿ndices or quadratics...﻿﻿

Im doing all the maths stuff along aide my course. I just havent done it, in so long i find it hard to remember lmao.

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30 minutes ago, Madgemade said:

Ahh, because of the resisters I was think of resistance and I don't think you can have negative resistance resister. Negative current yes, I is current so yeah should have realised that one. Hopefully OP sees how to do the simulations equations, in math class they were much harder than that, often with indices or quadratics...

I rechecked my stuff, you got the right answer. I swapped a - for a +. Typical...

<Make me a sandwich.> <No! Make it yourself!> <Sudo make me a sandwich.> <FINE.> What is scaling and how does it work? Asus PB287Q unboxing! Console alternatives :D  CoC F.A.Q Beginner's Guide To LTT (by iamdarkyoshi)

Sauron'stm Product Scores:

Spoiler

Just a list of my personal scores for some products, in no particular order, with brief comments. I just got the idea to do them so they aren't many for now

Don't take these as complete reviews or final truths - they are just my personal impressions on products I may or may not have used, summed up in a couple of sentences and a rough score. All scores take into account the unit's price and time of release, heavily so, therefore don't expect absolute performance to be reflected here.

-Lenovo Thinkpad X220 - [8/10]

Spoiler

A durable and reliable machine that is relatively lightweight, has all the hardware it needs to never feel sluggish and has a great IPS matte screen. Downsides are mostly due to its age, most notably the screen resolution of 1366x768 and usb 2.0 ports.

-Apple Macbook (2015) - [Garbage -/10]

Spoiler

From my perspective, this product has no redeeming factors given its price and the competition. It is underpowered, overpriced, impractical due to its single port and is made redundant even by Apple's own iPad pro line.

-OnePlus X - [7/10]

Spoiler

A good phone for the price. It does everything I (and most people) need without being sluggish and has no particularly bad flaws. The lack of recent software updates and relatively barebones feature kit (most notably the lack of 5GHz wifi, biometric sensors and backlight for the capacitive buttons) prevent it from being exceptional.

-Microsoft Surface Book 2 - [Garbage - -/10]

Spoiler

Overpriced and rushed, offers nothing notable compared to the competition, doesn't come with an adequate charger despite the premium price. Worse than the Macbook for not even offering the small plus sides of having macOS. Buy a Razer Blade if you want high performance in a (relatively) light package.

-Intel Core i7 2600/k - [9/10]

Spoiler

Quite possibly Intel's best product launch ever. It had all the bleeding edge features of the time, it came with a very significant performance improvement over its predecessor and it had a soldered heatspreader, allowing for efficient cooling and great overclocking. Even the "locked" version could be overclocked through the multiplier within (quite reasonable) limits.

-Apple iPad Pro - [5/10]

Spoiler

A pretty good product, sunk by its price (plus the extra cost of the physical keyboard and the pencil). Buy it if you don't mind the Apple tax and are looking for a very light office machine with an excellent digitizer. Particularly good for rich students. Bad for cheap tinkerers like myself.

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Posted · Original PosterOP

Ngl i really dont get how i get these answers and how i can answer the question? Is there any youtube videos to follow?

I used this one, but i dont believe i can solve the equation the way he did it.

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Posted · Original PosterOP

To answer my assignment questions,

Task A)

The current in the resistors would be as follows yes?

R1= 0.07

R2= 0.9

RL=0.97

And Task B?

Power dissapated would be 25 volt? Or no?

If i am wrong how would i answer this question?

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Posted · Original PosterOP

Right, i just read about the second question.

P = I2R?

So

0.972 x 9 =8.47W?

Am i right or no?

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Posted · Original PosterOP

Anyone lol?

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You can always check if you're right using circuit simulators... click here tosee your circuit and move mouse over components for current and power: http://tinyurl.com/yah69dnd

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