simple circuit question

[Bluga]

In the diagram here, why is Vt = 3*4 = 12V ? What about the 16 ohm resistor?

 

[blahblah99]

it's 12V because you don't have a load. As soon as you drop a load on there, say call it Rload, your Vt becomes

Vt = (3A)*(4 Ohm) * Rload/(Rload+16Ohm) - simple application of voltage division.

 

[Bluga]

Thanks, but isn't the positive node of Vt connected to the 16 ohm resistor?

 

[Bluga]

oh ok i get it, thanks!

 

[blahblah99]

no... if you transform the current source and the 4 ohm, you get

-------5 ohms------
| |
---------------------------<----Vt
|
16 Ohms
|
|
4 Ohms
|
12V
|
gnd.

since no current is passing through any components, your voltage is just 12V. if you have a resistor at vt to ground, then the voltage would be different.