# How would I solve this Mixed Circuit?

#### Logan Batson

1. Homework Statement

The following circuit is given, and all voltage, current, resistance and power must be found for each resistor. I have found the following information:

Vsrc = ?
Isrc = .5A
Rsrc = ?
Psrc = ?

V1 = ?
I1 = .5A
R1 = ?
P1 = ?

V2 = 2.5V
I2 = .25A
R2 = 10
P2 = .625W

V3 = 2.5V
I3 = .25A
R3 = 10
P3 = .625W

V4 = 5V
I4 = .25A
R4 = 20
P4 = 1.125W

How would I solve for the information of R1?

2. Homework Equations

V = IR

3. The Attempt at a Solution

I originally had thought that V1 is 5V, as the current is the same as the simplified parallel section. If the voltage from the cells is constant, and half of the circuit uses 5V, then I had assumed the other section would use 5V as well, as both currents are the same.

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#### phinds

Gold Member
1. Homework Statement

The following circuit is given, and all voltage, current, resistance and power must be found for each resistor.

View attachment 235274

I have found the following information:
That makes it obvious that you have not provided a complete problem statement. WHERE have you "found" this information?

#### Logan Batson

That makes it obvious that you have not provided a complete problem statement. WHERE have you "found" this information?
The information given with the circuit is:

I1 = 0.5A
V3 = 2.5V
V4 = 5V
P3 = 0.625W

Sorry about not including this. Using Ohm's law, Kirchhoff's laws, and the equation P = VI, I had determined all other variables of the circuit using this information.

#### phinds

Gold Member
OK, so the circuit simplifies to R1 in series with a 10 ohm resistor that has 1/2 amp flowing through it and 5 volts across it. I don't see how this is enough information to tell anything about R1 and the voltage source --- they have a relationship, but you can't get numerical values. Are you sure this is all the info you were given?

EDIT: Oh, wait ... is it a requirement to get numerical values or is an algebraic expression OK?

#### Logan Batson

OK, so the circuit simplifies to R1 in series with a 10 ohm resistor that has 1/2 amp flowing through it and 5 volts across it. I don't see how this is enough information to tell anything about R1 and the voltage source --- they have a relationship, but you can't get numerical values. Are you sure this is all the info you were given?

EDIT: Oh, wait ... is it a requirement to get numerical values or is an algebraic expression OK?
An equation would work too! Thanks for helping

#### phinds

Gold Member
An equation would work too! Thanks for helping
OK. Can you get the equation? It should be really simple since you've got a simplified circuit that is two resistors and a power supply

#### Logan Batson

OK. Can you get the equation? It should be really simple since you've got a simplified circuit that is two resistors and a power supply
It should just be (Vt - 5) = 0.5(Rt - 10) right?

#### phinds

Gold Member
It should just be (Vt - 5) = 0.5(Rt - 10) right?
No, I think you are counting the equivalent resistor twice.

I get V - 5 = .5R1

#### Logan Batson

No, I think you are counting the equivalent resistor twice.

I get V - 5 = .5R1
Oh okay, I understand now. Thanks so much for your help