Potential Difference and Resistors

In summary, in this conversation, the speaker is trying to solve a problem involving three resistors in a circuit with an emf of 18.0 V. They use the equations V=IR and the loop rule to calculate the total current and determine that the voltage is the same throughout all circuits in a parallel combination. They also explain how to find the individual voltages and currents for each resistor.
  • #1
ihearyourecho
61
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 ! :)
 
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  • #2
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.
 
  • #3
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
 
  • #4
18 V is common across R1 and (R2 +R3) combination.
So I1 = 18/R1
And I2 = 18/(R2+R3)
 
  • #5
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!
 
  • #6
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.
 
  • #7
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
 
  • #8
Oh, right on man. Thanks for your help! I'm pretty sure I understand now.
 

1. What exactly is potential difference?

Potential difference, also known as voltage, is the difference in electric potential between two points in a circuit. It is measured in volts (V) and is a measure of the amount of energy required to move a unit of charge from one point to another.

2. How are potential difference and current related?

Potential difference and current are directly proportional to each other according to Ohm's law. This means that as the potential difference increases, the current also increases, and vice versa. However, this relationship is dependent on the resistance of the circuit.

3. What is the role of resistors in potential difference?

Resistors are components in a circuit that are designed to limit the flow of current. They do this by providing resistance to the flow of electricity, which in turn causes a drop in potential difference. This allows for the control and regulation of the current in a circuit.

4. How does the resistance of a material affect potential difference?

The resistance of a material is directly related to its potential difference. This means that as the resistance of a material increases, the potential difference across it also increases. This is because a higher resistance material requires more energy to move the same amount of charge through it.

5. Does potential difference always remain constant in a circuit?

In an ideal circuit, potential difference is constant throughout. However, in real-life circuits, there may be fluctuations in potential difference due to factors such as the resistance of the circuit, temperature changes, and other external factors. These variations can affect the overall performance of the circuit.

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