I am having some difficulties solving a combination circuits problem

[EddyBenzen122]

Homework Statement

The current in the 8 - ohm resistor in the drawing is 5 A. Find the current in the 20 ohm and 9 - ohm resistor.

Relevant Equations

V = IR

I'm having difficulties finding the current for a 9-ohm resistor only, not the 20-ohm

My attempt was to find the voltage of a 20ohm resistor which is V = (0.75A)(20-ohm) = 15V. I got the 0.75A by adding the currents of the two resistors (8-ohm and 16-ohm) together that were in parallel and it becomes the current that will flow through the 20-ohm resistor. After getting 15V, I don't know what to do next in order to find the current in the 9 - ohm resistor.
Also, look at the image for more information.

 

[haruspex]

Homework Statement:: The current in the 8 - ohm resistor in the drawing is 5 A. Find the current in the 20 ohm and 9 - ohm resistor.
Relevant Equations:: V = IR

I'm having difficulties finding the current for a 9-ohm resistor only, not the 20-ohm

My attempt was to find the voltage of a 20ohm resistor which is V = (0.75A)(20-ohm) = 15V. I got the 0.75A by adding the currents of the two resistors (8-ohm and 16-ohm) together that were in parallel and it becomes the current that will flow through the 20-ohm resistor. After getting 15V, I don't know what to do next in order to find the current in the 9 - ohm resistor.
Also, look at the image for more information.

What other voltages can you determine?

 

[EddyBenzen122]

What other voltages can you determine?

4Volts from the parallel circuits with an 8-ohm and 16 - ohm

 

[haruspex]

4Volts from the parallel circuits with an 8-ohm and 16 - ohm

So what is the voltage across the $9 \Omega$|| $18 \Omega$ pair?

 

[EddyBenzen122]

So what is the voltage across the $9 \Omega$|| $18 \Omega$ pair?

that's what I'm looking for in order to find its current next.

 

[haruspex]

that's what I'm looking for in order to find its current next.

What is the relationship between the voltages:
- across the 9Ω|| 18Ω pair
- across the 8Ω|| 16Ω pair
- across the 20Ω resistor
?

 

[EddyBenzen122]

What is the relationship between the voltages:
- across the 9Ω|| 18Ω pair

the voltages are the same for both resistors

- across the 8Ω|| 16Ω pair

the voltages are the same for both resistors

- across the 20Ω resistor

?

the voltage is the sum of the currents for the 8-ohm resistor and the 10-ohm resistor multiplied by the 20-ohm resistor.

 

[haruspex]

the voltages are the same for both resistors

I didn't ask how the voltage across one of a pair compared with the voltage across the other of the pair. I asked about the relationship between the voltage across the 9Ω|| 18Ω pair (taken as a pair), the voltage across the 8Ω|| 16Ω pair (taken as a pair) and the voltage across the 20Ω resistor. Three voltages, one relationship.

the voltage is the sum of the currents for the 8-ohm resistor and the 10-ohm resistor multiplied by the 20-ohm resistor.

I have no idea how you arrive at that.

 

[EddyBenzen122]

I have no idea why you're asking me about the relationships between them, are you just giving me a hint?

 

[haruspex]

I have no idea why you're asking me about the relationships between them, are you just giving me a hint?

Of course I am giving a hint!

Call the voltage at the right of the 20 Ohm resistor 0.
So what is the voltage at the right of the 9||18 pair?

What is the voltage at the left of the 20 Ohm?
So what is the voltage at the left of the 8||16 pair?
So what is the voltage at the left of the 9||18 pair?

 

[EddyBenzen122]

Of course I am giving a hint!

Call the voltage at the right of the 20 Ohm resistor 0.
So what is the voltage at the right of the 9||18 pair?
What is the voltage at the left of the 20 Ohm?
So what is the voltage at the left of the 8||16 pair?
So what is the voltage at the left of the 9||18 pair?

K, i got the voltages: 4volts for 8||16 pair, 15V for 20ohm, and 19V for 9||18 pair.
Are they correct?

 

[haruspex]

K, i got the voltages: 4volts for 8||16 pair, 15V for 20ohm, and 19V for 9||18 pair.
Are they correct?

Yes.

 

[sysprog]

Very nice @haruspex, and good going, @EddyBenzen122 . . .

 

[EddyBenzen122]

Yes.

Thanks for helping me, I really appreciate it!