Finding potential difference in a circuit

[songoku]

Homework Statement

Please see below

Relevant Equations

Kirchhoff Law

I have found part (a):
current on the left is 7/12 A from A to B
current on the middle is 5/36 A from F to C
current on the right is 13/18 A from D to E

For part (b), what is the meaning of V_BF? Is it V_B - V_F or V_F - V_B?

My attempt is:
V_BF = I₁ x R₁ - ε₁ = 7/12 x 4 - 1.5 = 5/6 V

Is it correct?

Thanks

 

[Rap]

Homework Statement: Please see below
Relevant Equations: Kirchhoff Law

View attachment 370977

I have found part (a):
current on the left is 7/12 A from A to B
current on the middle is 5/36 A from F to C
current on the right is 13/18 A from D to E

For part (b), what is the meaning of V_BF? Is it V_B - V_F or V_F - V_B?

My attempt is:
V_BF = I₁ x R₁ - ε₁ = 7/12 x 4 - 1.5 = 5/6 V

Is it correct?

Thanks

VBF is the voltage drop from point B to point F and yes, that's correct.

 

[Gavran]

For part (b), what is the meaning of V_BF? Is it V_B - V_F or V_F - V_B?

I am unsure of what to say here. There are those who will tell you that Vbf is equivalent to Vb - Vf, and there are those who will tell you that Vbf is equivalent to Vf - Vb. If your choice is Vbf=Vf-Vb, your calculations are correct. The points B and C are at the same potential, so you can check your result by calculating the potential difference across the resistor R2, which is Vcf. It must be the same as the potential difference Vbf. Points B and D are also at the same potential, so Vbf must be equal to Vdf too.

 

[songoku]

Thank you very much for the explanation Rap and Gavran