E=IxR

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brian john

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Leesburg, VA
Last night my 8th grade daughter asked me a question that had come up in her science class regarding the use of ?I? for current in electrical formulas. Her science teacher had no idea why. So my daughter (the one that seldom speaks up in class) said "My Dad knows everything about electricity, he'll know!?

Now I have always assumed it must have something to do with the Greek alphabet, much like the symbol for ohms. But I want a positive truthful answer. I have searched the web without any luck. Any help.
 
Re: E=IxR

Before ampereage had a name, the phrase used to describe what we now call amperage was called "intensity", hence the letter "I".

"Electromaotive Force" is "E", which is also known as "Voltage".
 
Re: E=IxR

Originally posted by ryan_618: Before ampereage had a name, the phrase used to describe what we now call amperage was called "intensity", hence the letter "I".
Now why did you have to do that? Tell the truth and all, or at least something that can be easily believed as though it were true. Shame on you. I was perfectly content not to know that, and to assume that the "I" stood for "I don't know why we use I." :D
 
Re: E=IxR

Intensity - wow, neat explanation.

But lets make it more complicated.
I is the letter represenation of a quantity (electric current). The units of this quantity are amps.

This is the same as:
P - quantity = power, measured in watts
R - quantity = resistance, measured in ohms
C - quantity = capacitance, measured in farads

d - quantity = diameter, measured in inches
l - quantity = length, measured in feet
c - quantity = speed of light, measured in m/sec

The problem comes from our desire to use measurement nicknames like: voltage, wattage and amperage and occasionally ohmage (but that kind of hurts).

Thankfully we do not use nicknames like "This morning the degreeage in Wisconsin was 10F".
 
Re: E=IxR

I edited out a person's post, as it contained an inappropriate joke along the lines of "guy humor that we wouldn't want the gals to hear." Let's keep the humor clean, or let's keep it out.
 
Re: E=IxR

I received the follwing lingk from another tech in my office.


C:\Documents and Settings\bgaquin.MAPS\Local Settings\Temporary Internet Files\OLK1D\Ohm's law calculation calculator calculate magic triangle tip online voltage volts resitor resistance amps amperes - sengpielaudio.htm

The symbol I comes from "International Ampere" and R from "Resistance", and U (= V or E)?
 
Re: E=IxR

That link won't help us. It points to a file on the hard drive of someone's computer. We can't get there from here, and thank goodness for that. :p
 
Re: E=IxR

Ohm?s law has four values which are

E- The first letter in Electromotive force
I- The first letter in Intensity of current
R- The first letter in Resistance
P- The first letter in Power

E or voltage if the amount of force it takes to push I or current through R or resistance and the resulting heat or energy is measured in P or watts.


For a free lesson in Ohm?s law click here.
 
Re: E=IxR

Originally posted by bphgravity:
Stop using "I" and start using "A" and these questions and confusion will go away.
what we really need is a new word for the grounded conductor. Too much confusion between that, ground, and neutral. Lets all just start calling it the fizzy and see it it catches on.
 
Re: E=IxR

Originally posted by jwelectric:
Ohm?s law has four values which are

E- The first letter in Electromotive force
I- The first letter in Intensity of current
R- The first letter in Resistance
P- The first letter in Power

E or voltage if the amount of force it takes to push I or current through R or resistance and the resulting heat or energy is measured in P or watts.
Nuh-uh JW,

Power and energy are not the same things. Power is the time rate of energy transfer, that is,

1 watt = 1 joule/second
1 joule = 1 watt-second

Now, how many joules in 1 KWH?

[ December 03, 2005, 11:29 PM: Message edited by: rattus ]
 
Re: E=IxR

Originally posted by rattus:
Originally posted by jwelectric:
Ohm?s law has four values which are

E- The first letter in Electromotive force
I- The first letter in Intensity of current
R- The first letter in Resistance
P- The first letter in Power

E or voltage if the amount of force it takes to push I or current through R or resistance and the resulting heat or energy is measured in P or watts.
Nuh-uh JW,

Power and energy are not the same things. Power is the time rate of energy transfer, that is,

1 watt = 1 joule/second
1 joule = 1 watt/second

Now, how many joules in 1 KWH?
Originally posted by brian john
Last night my 8th grade daughter asked me a question that had come up in her science class regarding the use of ?I? for current in electrical formulas.
Now we can keep this on an eight grade level or if you would like we can get involved in some calculus.
If you would care to check out the site I posted from NASA for the grade school children you can see I only quoted them.

Myself I have never saw the value of someone wasting their time in a lot of the bull that is required to be an electrical engineer unless they are planning on getting involved in the design of electronic equipment therefore I don?t spend a lot of time messing around with the crap. I just barley passed some of this junk as I see no need for it when doing electrical code applications. In my world a five volt amplifier would be useless unless it was part of a VFD and then I would just replace it or a PLC and again I would just replace the bad part and go about my business.

I will concede that your knowledge in the math of electronics is superior to mine with out future debate. Please don?t take offence at my outlook of the field of electronics and how it applies to the electrical engineer.
 
Re: E=IxR

JW,

No calculus needed here. No electronics either. Simply put, the distinction between power and energy is fundamental to all electrical systems.
 
Re: E=IxR

Rattus

I apologize for coming off so strong last night and bouncing so hard on the electronics side of the engineer?s degree.

I have taught classes for the past five years at the community college. I don?t have a Masters Degree so I cannot teach transfer students although I did teach a lot of the theory classes.

Over the last five years I have receive students that had failed out of the first year of the electronic classes that were working toward an Electrical Engineer degree. These were the most difficult students to work with as they were always coming to my classes mid way through the curriculum and I would have to redirect their way of thinking about circuit lay out.

I am working toward an Electrical Engineers degree and if it wasn?t for the theory classes that I taught I would have failed out. I can understand the reasoning behind some of the classes that I need to take and how they would at some point in time apply to the trade but, for the most part, I will never use any of what is being covered.

At the end of my last class the instructor ask us to write a short essay on what we had learned during his class. This essay will count as 25% of your final grade. He gave me full credit for my essay and I barley passed his course. He is a retired engineer himself.

A short summery of my essay:
Although the knowledge I have gained in this class could be applied in real life I will never use much of it. I have learned that if I burn approximately 178 calories I can produce enough energy for approximately one horse power or 746 watts of power.

In my post above I should have stated it a little different for those who are in the know but I was trying to keep it on an eighth grade level. Maybe I should have made the statement a little more like this.

The amount of energy consumed to generate enough voltage to push one amp through one ohm of resistance will result in one watt.

Again please accept my apologies for trashing those who were smart enough and have worked hard enough to obtain their engineering degree. A lot of the resentment I feel could be due to the difficulties I am having passing some of these classes and I assure you I am having a hard time with them especially the calculus. What does it matter that the pitcher throws a ball at 90 MPH. Home plate is 60 feet 6 inches from the pitcher. Where is the ball when it reaches 45 MPH? Who cares? The only thing that is important is, did the batter hit it or not.

One more time, please forgive me for trashing the Electrical Engineers for it is not their fault that the curriculum is as hard as it is (at least for me).
:)
 
Re: E=IxR

Originally posted by bphgravity:
"L" = inductance in henrys

"XL" = inductive reactance in ohms
To find the L (Henerys) divide the Xl by 2times pie times the frequency.

To one and all

anytime i go wrong please fell free to steer me in the right direction as i need all the help i can get in the theroy of electricity.
:)

Edited to add:
And the use of capitol letters when typing
:)

[ December 03, 2005, 01:13 PM: Message edited by: jwelectric ]
 
Re: E=IxR

I pulled a fast one.

I switched from electrical quantities to other commonly used quantities and units of measure to expand on my example.

There is no such thing as "International Current". If there was, how would it differ from "Indigenous Current".

The scientific and electrical worlds have had international quantities, symbols and units of measurement for over 100 years. Although there have been duplicate (slang) names and symbols for almost the same length of time. Very few quantities are identified based on the first letter of their English name, hence the situation of U and V
 
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