Solving Basic Circuit Problem: Find Voltage Across 10 Ohm Resistor

[Magnawolf]

Homework Statement

Find voltage across 10 ohm resistor.

Homework Equations

Ohm's law

The Attempt at a Solution

20 // 30 = 12
30 // 60 = 20

That's as far as I can get. The answer is 14.286.

 

[gneill]

While the 20 and 30 Ohm resistors are in parallel, the 30 and 60 Ohm resistors are not (the voltage source intervenes).

You'll need to pull out some circuit analysis method. There are several choices. What methods have you studied so far?

 

[Magnawolf]

Here's the solution to the problem.

It looks like the book did source transformation, which I didn't think was fair because this problem is before source transformation.

I know nodal analysis and mesh but I thought it was possible to do without them. I thought you could just find the R-total and then you could find the total current. I guess not?

 

[gneill]

Here's the solution to the problem.

It looks like the book did source transformation, which I didn't think was fair because this problem is before source transformation.

Yup, they did a source transformation (Norton) and then current division.

I know nodal analysis and mesh but I thought it was possible to do without them. I thought you could just find the R-total and then you could find the total current. I guess not?

You need more than simple resistor network reductions (parallel/serial) here. Nodal analysis would be a good choice.

 

[Magnawolf]

alright thanks