# super position worksheet question

#### Liav

Joined Jun 10, 2009
2
Hi all. I feel like I have a basic understanding of superposition, but keep crashing and burning on some of the worksheet questions. Question five from http://www.allaboutcircuits.com/worksheets/super.html ask us to find the current through the load.

Removing the current source. we get:

Total circuit resistance = R1 || RL + R2 = ~350.4 ohms
R1 || RL = 130.4 ohms.

Voltage across R1 || RL = (130.4/350.4) * 7.2 = 2.68 V
Current across RL = 2.68V / 1000 ohms = .00268 A

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Removing the voltage source we get:

Total resistance = R1 + R2 || RL = ~330.0 ohms
R2 || RL = 180.3 ohms
Total circuit volage = .004A * 330.3 ohms = ~1.3213 V
Voltage across R2 || RL = (180.3/330.3) * 1.3213 V = .721 V
Current across RL = .721V / 1000 ohms = .000721 A

Total current = .0034 A

The listed solution, however, is 6.623 mA.

Any insight into what I'm doing wrong here?

Regards,
Liav.

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#### bill2009

Joined Apr 17, 2009
31
isn't the resistance R2 + R1||Rload?