# Kirchoffs Voltage Law Understanding

1. Nov 21, 2015

### Ryan Walkowski

<< 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 im 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. Im hoping someone can explain using the example I have. Im 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

Last edited: Nov 21, 2015
2. Nov 21, 2015

### Staff: Mentor

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.

3. Nov 21, 2015

### Ryan Walkowski

Ive updated what i think is correct! If anyone can confirm

4. Nov 21, 2015

### Staff: Mentor

Looks okay.

5. Nov 22, 2015

### CWatters

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

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.