Electrical questions

[xebo]

1. Do transformers provide a constant source of "Power" or voltage?

1a. If power is measured by voltage and current, total voltage is relatively constant, and total current changes depending on how many loads you have on the circuit (in parallel), then how can power output be constant?

2. On a circuit that spreads the loads evenly between the different phases, is there any current on the neutral?

2a. (2 rephrased):If I want to minimize current on the neutral, should my aim be to ensure the current on each phase is as equal as possible, by ensuring the resistance (load) on each phase is as equal as possible?

3. If an appliance is "x watts" (Like a 30 watt bulb), does that mean it will fail if more power than 30 watts is run through it? Does that mean it was designed to run at 30 watts only? Does it mean that "if you put 120 volts (for example) through this resistor, it will experience a current flow resulting in 30 watts of power? Where do wattage ratings come from, and why do they exist?

3a. If I increase the voltage to an appliance (Like going from 120v to 240v), what will happen? Overload, fail to operate, operate faster/brighter/etc?

3b. If an appliance is listed at "30 watts", is this just an indirect way of measuring its resistance? Why aren't lightbulbs "480 ohm bulbs"? Why is the standard to measure in terms of power?

 

[George Stolz]

We are not going to do your homework for you. How about answering these questions and letting the conversation stem from the answers instead?

 

[mgookin]

I'll second that. Provide your answers and the basis of each answer and that very well may engage some constructive dialogue.

 

[xebo]

We are not going to do your homework for you. How about answering these questions and letting the conversation stem from the answers instead?

Grown man seeks to expand his knowledge in the electrical field, goes to Mike Holt's forum and asks some theory questions that might make him better at his job. Grown man is condescended to and treated like a high schooler who's trying to cheat on his "homework".

No, I don't have homework. Yes, I'm asking direct questions that confuse me. Yes, I expected legitimate answers from people who might know more than I do.

Very disappointed so far. Don't see myself posting here again. Thanks for nothing I guess?

 

[Ponchik]

Interesting to say the least that a grown man has come up with very specific questions that are usually home work or college class questions. I have been on this forum for some time and usually similar questions do not randomly come up but when they do it indicates the poster is a student that wants the test questions answered by someone else.

The forum does welcome students with open arms, and will help you find the answer if we see some initiative from the student.

by the way, we are all students here and we all learn together.

 

[Besoeker]

Grown man seeks to expand his knowledge in the electrical field, goes to Mike Holt's forum and asks some theory questions that might make him better at his job. Grown man is condescended to and treated like a high schooler who's trying to cheat on his "homework".

No, I don't have homework. Yes, I'm asking direct questions that confuse me. Yes, I expected legitimate answers from people who might know more than I do.

Very disappointed so far. Don't see myself posting here again. Thanks for nothing I guess?

I'm sure your charm will be missed.

 

[fmtjfw]

#2

#2

2. On a circuit that spreads the loads evenly between the different phases, is there any current on the neutral?

2a. (2 rephrased):If I want to minimize current on the neutral, should my aim be to ensure the current on each phase is as equal as possible, by ensuring the resistance (load) on each phase is as equal as possible?

The way to answer this question is to make it very simple. The old ways are usually simpler. Edison invented (or popularized) the three wire circuit. He was very interested in reducing the amount of copper used to ship electricity around a neighborhood. He use DC rather than AC because he considered AC the work of the devil (or of George Westinghouse). Now stick with me because there is a point to all of this.

Now he used DC with three wires, let's call them red (+), white (neutral), and black (-). They were hooked up to a generator (or maybe a pair of generators) as follows:

red    white  black
|       |       |
|<-120->|<-120->|
|<-----240----->|

Now electrical current is not only a number it is also a direction. If we have an ampere flowing from the generator on the red (+) wire we call it +1. If we have two amperes flowing on the black lead (-) we call it -2.

Now let's connect a 1 ampere load across red and white:

red    white  black
|       |       |
o--1A---o       |
|       |       |

Electricity flows in a circle so the +1 amps from the red wire becomes -1 amp in the white wire.

Now let's connect a 1 ampere load across white and black:

red    white  black
|       |       |
|       o--1A---o
|       |       |

Here white is more positive than black so +1 amps from the white wire becomes -1 amps in the black wire.

and with two loads:

red    white  black
|       |       |
o--1A---o--1A---o
|       |       |

Now we have +1 in red, -1 in black, and 0 in white since +1-1 = 0

With an unbalanced load:

red    white  black
|       |       |
o--1A---o--2A---o
|       |       |

Now we have +1 in red, -2 in black, and -1 in white since +1-2 = 0. Note the current in white is NOT 3

 

[K8MHZ]

1. Do transformers provide a constant source of "Power" or voltage?

A transformer doesn't 'provide' anything. It transforms one voltage to another or is used for circuit isolation. If it has it's loads in parallel, the voltage will stay pretty much the same at the loads, decreasing of course as the max output of the transformer is approached. If the loads are in series, the current will remain pretty much the same through the loads, dropping in the same manner as above for the same reason.

1a. If power is measured by voltage and current, total voltage is relatively constant, and total current changes depending on how many loads you have on the circuit (in parallel), then how can power output be constant?

Who told you power output would be constant?

2. On a circuit that spreads the loads evenly between the different phases, is there any current on the neutral?

Ideally, no.

2a. (2 rephrased):If I want to minimize current on the neutral, should my aim be to ensure the current on each phase is as equal as possible, by ensuring the resistance (load) on each phase is as equal as possible?

Yes.

3. If an appliance is "x watts" (Like a 30 watt bulb), does that mean it will fail if more power than 30 watts is run through it? Does that mean it was designed to run at 30 watts only? Does it mean that "if you put 120 volts (for example) through this resistor, it will experience a current flow resulting in 30 watts of power? Where do wattage ratings come from, and why do they exist?

You will also notice a voltage rating. Let's say it's 120. That means with 120 volts applied, 30 watts of power will be used. The ratings come from design and test measurements of prototypes. They exist for several reasons. Proper application and expected power use are just a couple.

3a. If I increase the voltage to an appliance (Like going from 120v to 240v), what will happen? Overload, fail to operate, operate faster/brighter/etc?

Failure eventually, for sure. Prior to that, overload, faster, brighter, smoke coming out then failure. Sometimes it happens rapidly.

3b. If an appliance is listed at "30 watts", is this just an indirect way of measuring its resistance? Why aren't lightbulbs "480 ohm bulbs"? Why is the standard to measure in terms of power?

No, watts are a measure of true power. The resistance of a filament changes as the bulb heats up. Another reason to list the power is because that is what the electric company charges us for. Not Volt Amps.

Welcome to the forum.

 

[Smart $]

Grown man seeks to expand his knowledge in the electrical field, goes to Mike Holt's forum and asks some theory questions that might make him better at his job. Grown man is condescended to and treated like a high schooler who's trying to cheat on his "homework".

No, I don't have homework. Yes, I'm asking direct questions that confuse me. Yes, I expected legitimate answers from people who might know more than I do.

Very disappointed so far. Don't see myself posting here again. Thanks for nothing I guess?

Your opinion. Your prerogative.

Your profile states you are an apprentice. Apprentices have homework and take tests. We cannot determine whether your questions are homework, test questions, or just plain ol' would-like-to-know queries. You have to consider you have no history here. We do not know you. You did not even introduce yourself. Grown man...??? Self-belief or introspection isn't the only means in obtaining that status. I imagine I am substantially older than you... and in some ways, I am still yet to be a grown man (hopefully I can maintain that characteristic for a few more years ).

Couple that with most everyone knowing the first comment from a unknown person lacking integrity when his/her character is in doubt or questioned is "Trust me..." or some other defensive muttering. What was that you were saying...?

So trust me , you are not making any friends here to date.

 

[K8MHZ]

If this rule is not still in effect, will someone please enlighten me?

[h=2]

Treatment of New Members[/h]

To all forum members, I am formally requesting that you no longer publicly question new members qualifications for posting here.

Keep in mind that all new member posts have already been approved by a forum moderator before they show up on the forum.

If you feel a new member is over their head please exercise one of two options.

1) Notify one of the Moderators, I suggest you send a PM to one of us with a description of the problem you see with a post. We will gladly discuss it with you.

2) Do nothing, ignore the post and move on.

The reasons for this should be self evident, we are going to chase away new members if they feel they have to justify their qualifications with the entire membership at large.

Not to mention many times it is just plain rude.

Bob
2007 Chief Moderator Mike Holt Forum​

Last edited by iwire; 02-04-08 at 03:25 PM.
​

 

[augie47]

K8MHZ:
Your point is well taken, but from my viewpoint, and I believe that of other mods, his original post was approved so he was allowed to post. In allowing his post , a moderator, simply noted a long standing policy as to how we handle "homework" type questions...a policy which I feel has strong merit as noted in subsequent posts.
I would be hard-pressed to believe the original post was not based on some type test or teaching means. Those are not questions or wording that normally just pop up in ones head.
The original posters reply in post #4 did not, IMHO, improve the situation or his standing.
Perhaps in this incidence the procedure used did not fit the circumstances, but all in all it has proven to be a valid path.
Truthfully, from his response, I would have to say, again IMO, nothing lost.

 

[iwire]

K8MHZ:
Your point is well taken, but from my viewpoint, and I believe that of other mods, his original post was approved so he was allowed to post. In allowing his post , a moderator, simply noted a long standing policy as to how we handle "homework" type questions...a policy which I feel has strong merit as noted in subsequent posts.

I had tried to respond to K8MHZs post but could not find the right way to put it. I thank you Gus for expressing it nicely for me.

 

[cadpoint]

Google is and can really be your friend. You can use the Image part of it and ?diagram (some of your phases)". One can get some single line diagrams of the subject matter.

Transformers can be of all types. In general yes, they are used to transform Voltage, but they can be also used to transform Amps. An example is a elevator transformer where AC is changed to DC and it bumps up the Amps, it's unusual in the field but does exist.

You have to remember that a simple A=B/C ratio problem can be used / associated when thinking about transformers, and in most all cases of other electrical problems.

In the simplest sense one can use some word substitution to the above ratio problem.
Consider (in the simplest sense)

Power = Watts
I = Amps
E = Volts
Resistance = Ohms

So, it could be W = A/V or P = I/E ,all one in the same! Notice that I'm not mixing the two sides of the equal sign above but in the field one might get a mix of information.

Easy enough to remember, you have abeach, you might have a PIER and WAVO's. One might have one or the other...

You can also study the Ohms Wheels where one can use other aspects of given electrical information to help get to a answer. There can well be other aspects to all the terms listed or presented and are usually reserved forhigher powers (pun intended) like
Engineers and Designers. Ohms wheel points out some of these various aspects. In you case remember whatthe problem is, solve the situation accordingly.

Another good direct overview of dealing with the electronic maganetic spectrum is http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html

Welcome to the Forum!

 

[K8MHZ]

K8MHZ:
Your point is well taken, but from my viewpoint, and I believe that of other mods, his original post was approved so he was allowed to post. In allowing his post , a moderator, simply noted a long standing policy as to how we handle "homework" type questions...a policy which I feel has strong merit as noted in subsequent posts.
I would be hard-pressed to believe the original post was not based on some type test or teaching means. Those are not questions or wording that normally just pop up in ones head.
The original posters reply in post #4 did not, IMHO, improve the situation or his standing.
Perhaps in this incidence the procedure used did not fit the circumstances, but all in all it has proven to be a valid path.
Truthfully, from his response, I would have to say, again IMO, nothing lost.

Understood. My perspective may be different than yours.

I didn't start my formal apprenticeship until I was 36. Prior to that, I had years of experience in the electrical field, most of it wrought with misinformation.

There were many things I was puzzled about that was not related to our homework. Also, we only had school for part of the year. I could see myself asking questions similar to the OP's and I also would have likely put them into a numbered question format. I still do that from time to time.

Questions did and still do just 'pop into my head'.

Would it not have been better to just ask if the question was homework related? If we have a rule about not answering homework questions, then why was the question allowed by the moderators? The OP stated the questions were not homework related and I don't think there is any evidence to the contrary.

My take may be a bit different if this was a post that was not moderated.

It is my humble personal opinion that allowing posts from brand new members that may incite negative responses should not be the forum's equivalent to throwing them to the lions.

Pardon me for going against the grain and making an attempt to answer the OP's questions.

 

[infinity]

The OP has no context or explanation as to why the questions are being asked. It sounded like a homework questions to me and to others. Grown men should have thicker skin.

 

[mgookin]

I thought a moderator only checks to make sure it is not a bot posting a question to allow a newbie's first post to display.

I've seen plenty of first timers get through, then discover they're DIY's doing dangerous tasks and then the thread gets locked afterwards.

To make the statements that we don't do your homework seemed, and still seems, indicated based on what was posted thus far. OP came back with a rant; he must have been offended being categorized as a student. His profile does say apprentice and that is a student.

I don't think we lost much on this one. Chalk it up to whatever column that goes in. Overall newbies are received with open arms, warm welcomes, smiles and all that. One slips and it's not a big deal.

 

[Ponchik]

I don't know if the first question does get moderated, but if it does then why are DIY questions allowed to get posted and then locked?

If the above is true, IMO the question should have not been posted.

 

[augie47]

If we have a rule about not answering homework questions, then why was the question allowed by the moderators? The OP stated the questions were not homework related and I don't think there is any evidence to the contrary.

Pardon me for going against the grain and making an attempt to answer the OP's questions.

Unable to answer all your questions, but we allow those type questions quite often and almost always post a "disclaimer" such as the one George posted. In 99% of the cases it seems to work well. There will always be exceptions. IF this is one of the exceptions, it might have gone better if the posters reply had not been as caustic.
Code related questions where the poster has "no idea" are commonplace, but "theory" type questions are very very often related to homework and thus are handled differently. Answering a student's questions is a disservice to the student as was pointed out earlier in the thread.
You read it differently which is fine and no one objected to your answering. I did not attempt to answer because, as Infinity stated, the OP did not have much of an explanation, more of a rant, and still made no attempt to show his line of thought in regard to the subjects.

 

[infinity]

Before a post hits the open forum a moderator will look at the new poster's profile to see if they're within the guidelines of the forum. Sometimes the profiles aren't explicit and we will ask for clarification from the person posting. Other times it takes a few posts before we can accurately determine if the poster is genuine. The moderators do quite a bit of work behind the scenes to keep the forum up to it's historically high standard.

 

[fmtjfw]

I tried not to answer his question, but to guide him on a method that would begin to answer the question.