- #1

Jarvis323

- 976

- 847

Attached is the model.

Find Vx and Vy.

The total resistance is 10 ohms, and the circuit elements are all in series. So 2 Amps of current is flowing in the direction of the arrow in the diagram across all elements, Vtotalsrc = (to the voltage from the current source and the voltage from the voltage source) must be 20 so that I = V/R = 2 Amps.

The way that I looked at it, Vy must be -2 volts. This way, The voltage from the current source reduces the overall current by -2 volts, putting it at 20 volts, and the current (flowing from high potential to low potential) is in the direction of the arrow on the current source. This would put Vx at 8 volts.

Anther student has the book that the problem is out of, and the solution it gives is Vy = 38 volts. Then, I = (18 - 38) / 10 = -2A. In other words, you get 2 Amps flowing in the opposite direction of the arrow in the picture.

Most people were trying to solve this problem, by knowing that there is a 10V voltage change across both the lower two resistors and upper two. But you need to know the direction of the voltage drop/gain. So you have to draw a few plus signs. The choices you make then dictate if you get Vy = 38, or Vy = -2. So if you went this approach, how do you determine the direction of the voltage drop across the resistors? If you choose to follow that the voltage drop is in the direction of the current which I would have done, then you get Vy = -2V.

Any thoughts, or confirmation that the book is wrong would be helpful. Thank you.

Find Vx and Vy.

## The Attempt at a Solution

The total resistance is 10 ohms, and the circuit elements are all in series. So 2 Amps of current is flowing in the direction of the arrow in the diagram across all elements, Vtotalsrc = (to the voltage from the current source and the voltage from the voltage source) must be 20 so that I = V/R = 2 Amps.

The way that I looked at it, Vy must be -2 volts. This way, The voltage from the current source reduces the overall current by -2 volts, putting it at 20 volts, and the current (flowing from high potential to low potential) is in the direction of the arrow on the current source. This would put Vx at 8 volts.

Anther student has the book that the problem is out of, and the solution it gives is Vy = 38 volts. Then, I = (18 - 38) / 10 = -2A. In other words, you get 2 Amps flowing in the opposite direction of the arrow in the picture.

Most people were trying to solve this problem, by knowing that there is a 10V voltage change across both the lower two resistors and upper two. But you need to know the direction of the voltage drop/gain. So you have to draw a few plus signs. The choices you make then dictate if you get Vy = 38, or Vy = -2. So if you went this approach, how do you determine the direction of the voltage drop across the resistors? If you choose to follow that the voltage drop is in the direction of the current which I would have done, then you get Vy = -2V.

Any thoughts, or confirmation that the book is wrong would be helpful. Thank you.