Ohms Law Pie Chart_What's your memory Aid?

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pcsailor

pcsailor

Member
Location
Minneapolis
Hi All,
This is my first post here. I have 20+ years of electrical experience but it's all been Federal and international time. I am taking the Master Electricians test in Minnesota soon and unfortunately, have never used the NEC book. It's never been required in my career. So I am a systems and operational engineer with a lot of troubleshooting experience, a lot of 440VAC, I've had 4160VAC motors, managed junior engineers, but have done very little new installations nor electrical designing.
I am saying this because I've read through previous posts about this subject and if you're going to answer with "you should know your algebra", don't waste your time. Your not helping anyone reading this.
I know we can write out EIR and PIE and do the abstract math to get the Ohms Law Pie Chart.
But I'm not a math genius and my confidence to be sure I have the squared numbers and square roots correct, when I'm about to take a test my career and family income depends on, is not there.
So I want to present how I have figured out how to remember the entire Ohms Law Pie Chart in a simple way.
I would like some feedback to simplify it further, or poke holes in it, or show me a simpler way you use.
My objective is to walk into the test, quickly write out the chart on scrap paper, write other important formulas, and then go through the entire test knocking out the easy questions first. Hopefully, ideally, less then an hour and enough answered to pass or at least get me pretty close with hours left to work out the difficult questions.
I've got a career of successful testing this way.
So here is my system:
One only needs to remember this:
  • 2 Multiplications
  • 2 Square Roots
  • 4 Divisions
  • 4 Squared numbers
,...and with some repetitive paperwork, handwriting this out many times, I've got the chart memorized in my head.
 
GeorgeB

GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
From when I was 10 or 11 years old, I think ...

Rabbit, Eagle, Indian

Rabbit sees eagle over indian, r=e/i
eagle sees indian chasing rabbit, e=ir
indian sees eagle over rabbit, i=e/r

you have to remember (memorize) p=ei, then can substitute above for eagle or indian to get e*e/r (e^2/r) and i*i*r (i^2*r)
 
Besoeker

Besoeker

Senior Member
Location
UK
pcsailor said:
Hi All,
This is my first post here. I have 20+ years of electrical experience but it's all been Federal and international time. I am taking the Master Electricians test in Minnesota soon and unfortunately, have never used the NEC book. It's never been required in my career. So I am a systems and operational engineer with a lot of troubleshooting experience, a lot of 440VAC, I've had 4160VAC motors, managed junior engineers, but have done very little new installations nor electrical designing.
I am saying this because I've read through previous posts about this subject and if you're going to answer with "you should know your algebra", don't waste your time. Your not helping anyone reading this.
I know we can write out EIR and PIE and do the abstract math to get the Ohms Law Pie Chart.
But I'm not a math genius and my confidence to be sure I have the squared numbers and square roots correct, when I'm about to take a test my career and family income depends on, is not there.
So I want to present how I have figured out how to remember the entire Ohms Law Pie Chart in a simple way.
I would like some feedback to simplify it further, or poke holes in it, or show me a simpler way you use.
My objective is to walk into the test, quickly write out the chart on scrap paper, write other important formulas, and then go through the entire test knocking out the easy questions first. Hopefully, ideally, less then an hour and enough answered to pass or at least get me pretty close with hours left to work out the difficult questions.
I've got a career of successful testing this way.
So here is my system:
One only needs to remember this:
  • 2 Multiplications
  • 2 Square Roots
  • 4 Divisions
  • 4 Squared numbers
,...and with some repetitive paperwork, handwriting this out many times, I've got the chart memorized in my head.
Click to expand...

Welcome from me and I wish you well with that test.

I can't offer easier solutions than those already presented by Larry.
Some things you just remember from frequent use. But, if a pie chart helps, go for it.
 
kwired

kwired

Electron manager
Location
NE Nebraska
pcsailor said:
Hi All,
This is my first post here. I have 20+ years of electrical experience but it's all been Federal and international time. I am taking the Master Electricians test in Minnesota soon and unfortunately, have never used the NEC book. It's never been required in my career. So I am a systems and operational engineer with a lot of troubleshooting experience, a lot of 440VAC, I've had 4160VAC motors, managed junior engineers, but have done very little new installations nor electrical designing.
I am saying this because I've read through previous posts about this subject and if you're going to answer with "you should know your algebra", don't waste your time. Your not helping anyone reading this.
I know we can write out EIR and PIE and do the abstract math to get the Ohms Law Pie Chart.
But I'm not a math genius and my confidence to be sure I have the squared numbers and square roots correct, when I'm about to take a test my career and family income depends on, is not there.
So I want to present how I have figured out how to remember the entire Ohms Law Pie Chart in a simple way.
I would like some feedback to simplify it further, or poke holes in it, or show me a simpler way you use.
My objective is to walk into the test, quickly write out the chart on scrap paper, write other important formulas, and then go through the entire test knocking out the easy questions first. Hopefully, ideally, less then an hour and enough answered to pass or at least get me pretty close with hours left to work out the difficult questions.
I've got a career of successful testing this way.
So here is my system:
One only needs to remember this:
  • 2 Multiplications
  • 2 Square Roots
  • 4 Divisions
  • 4 Squared numbers
,...and with some repetitive paperwork, handwriting this out many times, I've got the chart memorized in my head.
Click to expand...

If you get the P=IE and E=IR memorized there isn't much else you need to know for typical electricians exams.

Not being a math wiz is one thing, but to solve for any missing value in those formulas should be able to be done by anyone that finished high school and has any care about being any kind of success at anything.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
kwired said:
If you get the P=IE and E=IR memorized there isn't much else you need to know for typical electricians exams.
Click to expand...
Right. Just make the two pies like I posted and cover the unknown with your finger, exposing the right formula.
 
I

Ingenieur

Senior Member
Location
Earth
kwired said:
If you get the P=IE and E=IR memorized there isn't much else you need to know for typical electricians exams.....
Click to expand...

this^^^^

I'll add
for 3 ph P = sqrt3 IE
and understand what they mean

everything else can be derived
P = IE
E = IR
plug E into the P equation
P = I IR = I^2 R
the same can be done for I = E/R
P = E^2/R

imo those pie charts, etc, make it confusing
 
junkhound

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
Besoeker said:
Welcome from me and I wish you well with that test.


Some things you just remember from frequent use. .
Click to expand...

+1 on welcome and best performance on test.

Very true on frequent use.

if Infrequent: If somebody laid a 100 pound note on the table and asked me to recite or write the 4 Maxwell's equations, pretty sure I'd get at least 3 of 4 WRONG!.
 
M

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
Don't forget to include Power factor for AC. In the real AC world where most of us work, Pf is almost never 1.0
 
junkhound

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
Besoeker said:
Thank you, sir.


If someone did that to me I'd accuse them of being a forger - and not a very good one at that............:D
Click to expand...

Had to look it up ----£100 notes were last used by the Bank of England in 1945.

At least I dinna say Euro <G>

 
kwired

kwired

Electron manager
Location
NE Nebraska
meternerd said:
Don't forget to include Power factor for AC. In the real AC world where most of us work, Pf is almost never 1.0
Click to expand...
Power factor isn't something you typically need to know much about for electrician licensing exams. Most calculations you would be doing are in VA. Sizing of conductors and overcurrent protection is according to the A (in VA) and not watts. Not saying you can't get an occasional question that has power factor involved - but probably not enough questions would be this way to fail the test if they were the only ones you did not know how to answer.
 
Besoeker

Besoeker

Senior Member
Location
UK
kwired said:
Power factor isn't something you typically need to know much about for electrician licensing exams. Most calculations you would be doing are in VA. Sizing of conductors and overcurrent protection is according to the A (in VA) and not watts. Not saying you can't get an occasional question that has power factor involved - but probably not enough questions would be this way to fail the test if they were the only ones you did not know how to answer.
Click to expand...
I can see the sense in that. You don't have to be a circuit designer to be an electrician.
 
G

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
junkhound said:
+1 on welcome and best performance on test.

Very true on frequent use.

if Infrequent: If somebody laid a 100 pound note on the table and asked me to recite or write the 4 Maxwell's equations, pretty sure I'd get at least 3 of 4 WRONG!.
Click to expand...
But in all fairness, Maxwell is a lot more complicated than V=IR and P=VI, if I remember correctly.
 
junkhound

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
ggunn said:
But in all fairness, Maxwell is a lot more complicated than V=IR and P=VI, if I remember correctly.
Click to expand...

yeah, only one ah remember fer sur is upside down triange dot B = zero... another may be triangle X something = zero also :(
 
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