• Support PF! Buy your school textbooks, materials and every day products Here!

Finding the current and voltage for each resistor

1. Homework Statement
Moderators note: link removed. All images should be uploaded to PhysicsForums.
yodyWjB.jpg


2. Homework Equations
V=IR
Series in parallel
Series in current

3. The Attempt at a Solution
I managed to get the current and voltage of R1 and R2. I've been trying to get the next one R3, but haven't had success. I tried following the drawing, but couldn't figure out what I'm doing wrong. I thought that the current of R1 would be the current of R3. But I checked it against the solutions and it is incorrect.
 

Attachments

Last edited by a moderator:

.Scott

Homework Helper
2,388
819
The current through R2 plus R3 will equal the current in R1.
The current through R4 plus R5 will equal the current in R3.

Reading your work, all of your resistance calculations are correct.
 

.Scott

Homework Helper
2,388
819
Your only mistake so far is thinking that the current through R1 and R3 are equal.
 
Why does the current through R2 and R3 equal the current in R1? Does it have to do with the junction? And then I can't figure out R4 and R5 since I am unsure of what rule to follow. I figured out R3 would be I=.15, R=.75 .
Also, the reason I thought R1 and R3 current would be equal was because of the rule that in series currents are the same. But i guess R2 interrupts that rule?
 

.Scott

Homework Helper
2,388
819
Here's the rule: At any junction, there will be as much current flowing in as there is flowing out.
It in and out are given opposite signs (plus/minus), then the current at the junction will always add up to zero.
 
50
9
Prescripted, it seems you are new to circuits. It generally takes a while to realize that the assignment of the term "current" to the flow of charges was quite accurate. Thinking of a river can help you understand. After that it might be better to forget thinking of the flow of water. It does not apply to well to all cases. But it does here.

Assume we are talking about positive charge carriers. That way (as opposed to how electrons flow) the current comes out of the battery and heads for R1. After going thru R1, the charges have a choice. The current divides, some going thru R2 and some go thru R3. That is why the current through R2 + the current thru R3 equal the current in R1. Think of a river with a large island in it. Some of the water goes left, the rest goes right.
 

Related Threads for: Finding the current and voltage for each resistor

Replies
3
Views
1K
Replies
8
Views
22K
Replies
3
Views
558
Replies
9
Views
3K
  • Last Post
Replies
11
Views
1K
Replies
1
Views
1K
Replies
16
Views
150
Top