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April 18, 2014

April 18, 2014

Posted by **Lynn** on Saturday, February 5, 2011 at 11:05am.

R2= 20 ohm

R3= 50 ohm

R4= ???

R1, R2, R3 and R4 are connected in parallel across a 120 V "power" supply to generate a current of 21 Amps. The value of R4 is most nearly _____ ohms.

0, 5, 10, 16, 100, 200, 300

I think 5 ohms, but I'm not sure...In need of some assistance, please

- Physics-Please help -
**drwls**, Saturday, February 5, 2011 at 11:14amR(combined) = 120/21 = 5.71 ohms

1/5.714 = 1/10 + 1/20 + 1/50 + 1/R4

= 0.175 + 1/R4

0.175 = 1/R4 + 0.170

1/R4 = 0.005

R4 = ___

It's not 5 ohms

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