Basic Theory

[rbethke]

If you have the question: What is the conductor power loss in watts for a 10 AWG conductor that has a voltage drop of 3 % and carries a current flow of 24A? Does the information in this text tell you what voltage is being used? Or can you arrive at the voltage used from this info.
Thanks, rbethke

 

[George Stolz]

No, it's a bad question.

 

[LarryFine]

RB, welcome to the forum!

No, it's a bad question.

Bad question! Bad!

 

[charlie b]

The question is short by one key piece of information. There are three unknown quantities: The power (which is what the question asks for), the voltage, and the length of the conductor. I can come up with two independent equations that relate these three unknowns. I need a third equation, or I need to make one of the unknowns known. Tell me either the voltage or the length of the conductor, and I can tell you the power.

Bad question.

Welcome to the forum.

 

[resistance]

I also agree, it's a bad question.

Is this a test question?:roll:

 

[Pierre C Belarge]

It is not only a poorly worded question, but totally not necessary for an inspector to know.
I have noticed the test provider companies, who also provide study questions, are producing terrible test questions. I think they are doing what everyone else is trying to do. Increase the bottom line. Only, they are not paying close attention to the needs of the customer and they have not put enough time into reviewing the questions and answers for accuracy.

Also, the types of questions for the different types of tests can be better managed as well.

 

[rbethke]

Thank you for your support!

 

[weressl]

The question is short by one key piece of information. There are three unknown quantities: The power (which is what the question asks for), the voltage, and the length of the conductor. I can come up with two independent equations that relate these three unknowns. I need a third equation, or I need to make one of the unknowns known. Tell me either the voltage or the length of the conductor, and I can tell you the power.

Bad question.

Welcome to the forum.

Actually, yes AND no.

The power loss can be calculated as a percentage of the total load and it will be the same % for any voltage.

I - contstant
Ohm/foot - constant for 10 AWG
volt loss - constant %
voltage - when it is varied the voltage drop forces the cable length to be different
overall resistance - varies as per the cable length, linear
watt - I*I*R

What would also need to be known if it is a single phase to three phase load and the power factor.