Kirchoffs Voltage Law Understanding

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Discussion Overview

The discussion centers around understanding Kirchhoff's Voltage Law (KVL) in the context of a mock assessment paper. Participants are exploring how to apply KVL to specific examples, including the interpretation of potential changes indicated by arrows in circuit diagrams.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses difficulty in understanding how to derive answers related to KVL and seeks clarification using specific examples.
  • Another participant explains that arrows in circuit diagrams indicate changes in potential, with the direction of the arrow showing the increase in potential.
  • Some participants suggest writing equations that sum to zero to avoid mistakes with signs, emphasizing the importance of specifying the starting point in the analysis.
  • There are multiple approaches to writing KVL equations, with some participants proposing different methods for organizing the equations.

Areas of Agreement / Disagreement

Participants generally agree on the fundamental principle of KVL, but there are differing opinions on the best way to express and organize the equations. The discussion remains unresolved regarding the most effective method for applying KVL in practice.

Contextual Notes

Some participants note the importance of specifying starting points and the direction of potential changes, but there is no consensus on the best approach to writing KVL equations. The discussion includes various interpretations of how to apply the law to specific circuit examples.

Ryan Walkowski
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<< Mentor Note -- Thread moved as requested >>

I am trying to complete a mock paper for an upcoming assessment. The mock comes with the answers supplied in bold under the question yet I am having trouble understanding how the answers are obtained. I know that the law states that the sum of all emfs equals all the sums of the voltage drops and i have looked at several online articles but they seem to be very complex for what I need to understand. I am hoping someone can explain using the example I have. I am not sure how the arrows play a part in this either

EDIT: After much banging my head i have come up with the following.Can someone comment if this is correct and if there is a more excepted way of writing it out:

ΣV=0
B-E = -2V
E-D = +10V
D-C = -5V

BE+ED+DC = +3
∴ C-B = 3V

And

ΣV=0

B-E = -2
E-F = +8
A-B = 0

BE+EF+AB = +6
∴ F-A = 6V
IMG_6241.jpg
 
Last edited:
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The arrows depict a change in potential, increasing towards the arrow head. So for example, the arrow on the battery in the left bottom corner depicts an 8 V rise in potential across the battery going from node E to node F. Similarly, on the resistor connected from E to B there's a 2 V potential increase.

Kirchhoff's voltage law states that the sum of the potential changes around a closed path is zero.
 
Ive updated what i think is correct! If anyone can confirm
 
Ryan Walkowski said:
Ive updated what i think is correct! If anyone can confirm
Looks okay.
 
Ryan Walkowski said:
I know that the law states that the sum of all emfs equals all the sums of the voltage drops

gneill has already mentioned this but it's far better to think...

gneill said:
the sum of the potential changes around a closed path is zero.

and start by writing equations that sum to zero. For example you wrote..

BE+ED+DC = +3

I find I make fewer mistakes with the signs if I specify where I'm starting and write my equation to sum to zero like this..

Going anticlockwise from B..
BE + ED + DC + CB = 0

and then rearrange it to solve for the unknown CB.
 

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