# Going Crazy



## NH603 (Jan 21, 2018)

Hello all, I am still in my first year apprenticeship and going through school with an at home course which requires all books and study guides. Completed course #1102 now on #1101 (they do it backwards:/). About 90% completion of my current course/study guide and really stumped on some problems regarding basic parallel circuitry. Came here to see if anyone could help. I’ve literally tried solving this problem for 2.5 hours and don’t see what I am doing wrong. 

The problem is as followed:
A resistance of 14 ohms is connected in parallel with a coil that has a resistance of 4 ohms and a reactance of 12 ohms. The supply voltage is 120V. Find (a) the total current, (b) the power factor, and (c) the power taken by the circuit. 

A. Total current
a.) 8.5A
b.) 9.49A
c.) 14.58A
d.) None of the above

I can’t even get past (a) haha. I have already completed 50 equations regarding multiple circuits and for some reason this one is really messing me up. I’ve tried the following formulas. 

I= E/R 
I= E/X
Rt= R1 x R2/ R1+ R2 and get 3.11 ohms 
Then I divide the voltage by total risistance and get 38.5852 
Divide the voltage by the reactance and get 10
Then use formula
It= (Ir squared + il squared) square root
And get it= 38.5852 squared + 10 squared
it=1488.817 + 100 square root
it= 1588.817 square root
I total = 39.859 Amps

What am I doing wrong? I have plugged in more formulas than just this to try and get the correct answer but they’re all just not working. 

Thank you for your time and help!!


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## telsa (May 22, 2015)

C

You know A is wrong, straight off.


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## NH603 (Jan 21, 2018)

Thank you!! If you don’t mind sharing, how did you get this answer?


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## joebanana (Dec 21, 2010)

Why are you sure it isn't d.) None of the above? Just treat the reactance as a resistance.


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## telsa (May 22, 2015)

I play the odds.

Test writers have a chronic preference for using C as the correct answer.

'None of the Above' is VERY rarely used as a correct answer.

'A' is plainly wrong as you'll get past 8.5A just on the pure resistance leg.

And that's all the mental effort I'm willing to expend on what will prove to be an entirely wasted lesson in electrical engineering.

Questions like the OP's are designed to bother the students -- and set up a classroom discussion.

The OP has to realize that 'the system' is designed such that he's SUPPOSED to get the tough questions wrong. 

If he keeps showing up with 'perfects' -- the instructor is not impressed -- he's annoyed.

He (rightly) knows that the student has been 'cheating' via Internet forums.

The OP should realize that until recently all students were expected to figure things out with their own resources. 

This new trend is creating a MUCH dumber generation of talent.

The inability to divide by six -- in a microsecond -- in one's head -- is just one instance. 

All students should attempt to just shoot for getting 90% correct.

It's when you see your tests dropping down into the 70% zone that you should freak out.

When I was young, I was notorious for handing in perfect work. Trust me, I was hated for it. Don't follow my bad example.


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## NH603 (Jan 21, 2018)

Not trying to cheat just looking for some help. I don’t even need an answer just looking to see if someone can correct my work and point me in the right direction as I feel I have tried everything I can (clearly not because I haven’t got the correct answer). Not going to just guess either and just circle C. I need to show all my work or the credit isn’t given.


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