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harrisiqbal
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Homework Statement
A device can be modeled using a current source in
parallel with a resistor. This device was connected to
a 5[V] voltage source, as shown in Figure P2.3a), and
a current i5 of 0.93[A] resulted. The same device was
then connected to a 4[A] current source as shown in
Figure P2.3b), and a voltage v4 of –34[V] resulted.
Find the voltage v3 if a 3[Ω] resistor, as shown
in Figure P2.3c), is connected to the same device.
Homework Equations
V = iR, KCL, KVL, Sign Conventions
The Attempt at a Solution
[Freaking session expired and I lost whatever I wrote.. writing it again grrrrrr]
Link to picture of diagram:
http://www.mediafire.com/imageview.php?quickkey=lzuqgmqmitk&thumb=6
I define the device as the following:
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[ ]
[ ]
Current Source Resistor
[ ]
[ ]
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I connect this device to a 5 Volts voltage source for part a. And Apply KCL to get i2-i1 = 0.93 Amps. i2 is the current going through resistor, and i1 is the current by current source.
I move on to part b, and get equations [ probably the wrong ones ], but now I can't use anything from part a because the values would be different correct?
So I don't really understand how to solve this problem...
Help would be appreciated!____________________________________________________
***Update***:
Okay I understand it a bit better. For part a I use Kirchhoffs current law to find an expression for the current going through internal resistor. i2 = i1-0.93
I get an expression for Internal resistence: R = (V1 / i2) V1 is the 5 Volt power source in Part a.
Going into part b.
KCL law to get -i2 - i3 = 0 [ i3 is the given current source 4 Amps in part b]
so i2 = -4 amps
Voltage is given and current is i2. Resistence can be calculated to be 8.5 Ohms.
Part c:
Current Divider Rule:
lets me find i2[ which will be different because Resistor was added]
i2= -.396 Amps
V3____________________________
I have another QUICK question unrelated to the above problem.
If a question states that there is a device that is modeled using an ideal voltage source in series with a resistance. And that device is connected to a voltage source in the schematic. Then there will be TWO Voltage sources CORRECT? One inside the device and one that the device is connected to?
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