[Highschool Physics] Kirchoff's Rules

  • Thread starter 4Phreal
  • Start date
  • #1
17
0

Homework Statement



http://imgur.com/XXPWbCN

Homework Equations



∑ ΔV (closed circuit) = 0
∑ I (in) = ∑ I (out)

The Attempt at a Solution


So I know that the sum of the currents entering any junction in a circuit must equal the sum of the currents leaving that junction, and that the sum of the potential differences across all elements around any closed circuit loop must be zero. BUT this picture is so weird that I can't wrap my head around it. I think that I1 + I2 + I3 = 0, if one of those was negative which it can be. This means that (2) and (3) cannot be true. Then, solving for the potential difference equations, I got epsilon=-RI1+RI2 = -RI3+RI2, so I1R-I3R=0. So my answer would be both (1) and (5), but I'm not sure if that is correct. Could anyone help?
 

Answers and Replies

  • #2
1,540
135
So I know that the sum of the currents entering any junction in a circuit must equal the sum of the currents leaving that junction, and that the sum of the potential differences across all elements around any closed circuit loop must be zero. BUT this picture is so weird that I can't wrap my head around it. I think that I1 + I2 + I3 = 0, if one of those was negative which it can be. This means that (2) and (3) cannot be true. Then, solving for the potential difference equations, I got epsilon=-RI1+RI2 = -RI3+RI2, so I1R-I3R=0. So my answer would be both (1) and (5), but I'm not sure if that is correct. Could anyone help?

Correct .
 
  • #3
SammyS
Staff Emeritus
Science Advisor
Homework Helper
Gold Member
11,377
1,038

Homework Statement



http://imgur.com/XXPWbCN

Homework Equations



∑ ΔV (closed circuit) = 0
∑ I (in) = ∑ I (out)

The Attempt at a Solution


So I know that the sum of the currents entering any junction in a circuit must equal the sum of the currents leaving that junction, and that the sum of the potential differences across all elements around any closed circuit loop must be zero. BUT this picture is so weird that I can't wrap my head around it. I think that I1 + I2 + I3 = 0, if one of those was negative which it can be. This means that (2) and (3) cannot be true. Then, solving for the potential difference equations, I got epsilon=-RI1+RI2 = -RI3+RI2, so I1R-I3R=0. So my answer would be both (1) and (5), but I'm not sure if that is correct. Could anyone help?
Due to my OCD, I like the images to be visible -- or at least documented.

attachment.php?attachmentid=70601&stc=1&d=1402727871.jpg
 

Attachments

  • XXPWbCN.jpg
    XXPWbCN.jpg
    12.7 KB · Views: 373

Related Threads on [Highschool Physics] Kirchoff's Rules

  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
13
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
5
Views
3K
  • Last Post
Replies
1
Views
4K
  • Last Post
Replies
8
Views
24K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
2
Views
892
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
2
Views
10K
Top