Potential Difference and Resistors

AI Thread Summary
The discussion focuses on calculating the potential difference and current across three resistors in a circuit with an 18.0 V battery. The user initially miscalculates the total current and misunderstands the configuration of the resistors, mistaking the series and parallel arrangements. Clarification is provided that the voltage is the same across all branches in a parallel circuit, while current varies. The correct approach involves applying Ohm's law (V=IR) to each resistor, with specific calculations for the combined resistance of R2 and R3. Ultimately, the user gains a clearer understanding of the concepts involved in the circuit analysis.
ihearyourecho
Messages
61
Reaction score
0

Homework Statement



Suppose the three resistors in the circuit have the values R1 = 180, R2 = 220, and R3 = 350, and that the emf of the battery is 18.0 V
http://session.masteringphysics.com/problemAsset/1126258/3/5416321031_128.jpg

Find the potential difference across each resistor.

Find the current that flows through each resistor.



Homework Equations



V=IR

The Attempt at a Solution



These things really confuse me, but here is my shot:
V=IR
Itotal=18/(1/180+1/220+1/350)=.233

I also know that due to the loop rule, the sum of all of the potential differences is 0. Because of the junction rule, the current flowing into a junction must equal what's flowing out. I'm just not sure how I can figure out either the V or I across a resistor if I have two unknowns...

any help would be awesome ! :)
 
Physics news on Phys.org
Itotal=18/(1/180+1/220+1/350)=.233
This is wrong.
R2 and R3 are in series and R1 is in parallel with that combination.
 
Oh, wow, that definitely was wrong. Stupid mistake because I'm frustrated with this stuff I guess. Itotal=136.8

The problem is more of I'm not sure what to do next though
 
18 V is common across R1 and (R2 +R3) combination.
So I1 = 18/R1
And I2 = 18/(R2+R3)
 
So Voltage is the same throughout all circuits? Or just in parallel circuits? I'm more looking for the concept of the whole thing more than the answer right now. Thanks for your help so far!
 
Also, when it wants V1,V2,V3 and I enter 18,18,18, that is not correct.
When it wants I1, I2, I3 (In mA) and I enter 100, 81.8, 51.4, that also is not correct.
 
ihearyourecho said:
So Voltage is the same throughout all circuits? Or just in parallel circuits? I'm more looking for the concept of the whole thing more than the answer right now. Thanks for your help so far!
In the parallel combination the voltage is common across each branch.
In each branch current may be different.
In a branch if there more than one resistance, then
V = V1+ V1 + ...
In the given problem
I1 = V/R1
I2 = V/(R2 + R3).
V2 = I2*R2
V3 = I2*R3
 
Oh, right on man. Thanks for your help! I'm pretty sure I understand now.
 

Similar threads

Need help with a question on potential difference
Replies
7
Views
1K
Circuit with potential difference across battery being zero?
Replies
3
Views
1K
Finding the Current in a Resistor in a Closed Circuit
Replies
4
Views
2K
Calculating the voltage across capacitors and resistors with switches
Replies
2
Views
730
Sign conventions for Kirchhoff's loop rule
Replies
7
Views
1K
Understanding example in Wikipedia entry for open circuit voltage
Replies
3
Views
2K
The potential difference/EMF in RL circuits
Replies
6
Views
3K
Is voltage the same in parallel circuits with different resistance values?
Replies
2
Views
6K
Parallel Circuits - Joining 2 branches together
Replies
7
Views
2K
Circuit analysis: Six resistors and two batteries
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top