# Using Y to Delta Transformation to Find Currents

## Homework Statement:

Use a Y-to-Δ transformation to find the unknown quantities for the circuit.
Find:
1) io
2) i1
3) i2
4) power delivered by ideal voltage source

## Relevant Equations:

Shown below are the equations for delta to y transformations and vice verse. Also the current divider equation and Ohm's law.

Can someone explain why I can't simply use a current divider once I've found the equivalent resistance and source current for the entire circuit? This would look like i0 = 0.044*(113.53/210). Req = 113.53.

If it helps, the correct answers appear to be: i0 = 8.28 mA, i1 = 23.6 mA, i2 = 35.8 mA, P = 0.220 W.

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vela
Staff Emeritus
Homework Helper
The logic is: if you have a current divider circuit, then I = I_total (R/Req).

You don't have a current divider, so the formula doesn't apply.

You might try finding the Norton equivalent of the circuit connected to the 210-ohm resistor. You would then have a current divider. You'll find I_nort is not equal to the source current you calculated, and Rth is nowhere near Req.

The logic is: if you have a current divider circuit, then I = I_total (R/Req).

You don't have a current divider, so the formula doesn't apply.

You might try finding the Norton equivalent of the circuit connected to the 210-ohm resistor. You would then have a current divider. You'll find I_nort is not equal to the source current you calculated, and Rth is nowhere near Req.
Why don't I have a current divider for 210 ohm resistor? It is, after all, in parallel. And parallel circuits divide current up?

vela
Staff Emeritus
Homework Helper
In parallel with what?

In parallel with what?
40 and 20

vela
Staff Emeritus
Homework Helper