# Homework Help: Non-linear device problem

1. Jun 25, 2010

### jegues

1. The problem statement, all variables and given/known data
See figure

2. Relevant equations

3. The attempt at a solution

Again, see figure I tried something and it looked promising but the answer doesn't work out.

Any ideas?

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2. Jun 25, 2010

### vela

Staff Emeritus
Could you explain your reasoning to get the equation

$$\frac{1+v_Q/i_Q}{2+v_Q/i_Q} = 10$$

I don't see how you're applying Kirchoff's voltage law to get that.

3. Jun 25, 2010

### wwshr87

You know the 1 ohm resistor is in parallel with the 10V source, therefore the voltage across it is 10V. Now we can subtract from the 10V the drop across the other 1 ohm resistor which is 1*Iq, and subtract Vq. 10 - 1*Iq - Vq=0, we can plug in for Iq which is Vq^2+2*Vq. Solve for Vq, you'll obtain a positive and negative value but only the positive makes sense because of our polarity.

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4. Jun 26, 2010

### Zryn

When you combine the circuit resistances, first by adding the two in series, and then by calculating the two in parallel, you get a value of resistance (keep in mind SI units).

In your equations you say this resistance is equal to 10 volts by KVL.

$$\frac{1+v_Q/i_Q}{2+v_Q/i_Q} = 10$$

Resistance does not equal voltage.

5. Jun 26, 2010

### jegues

Thanks for the responses. I must have been out of it at the time putting resistance equal to voltage lol.

I understand now.

$$V_{q} = 2V$$