Quick Formula Confirmation

[Pete999]

kVA will always be greater than or equal to kW, because kVA is the hypotenuse (the long side, the one opposite the right angle) of the triangle.

The question says "dissipates" which means "consumes" or "uses up" or "turns into heat" 7.5kW of power... also the fact that it's in kW suggests that the intention of the question is that true power = 7.5kW.

If you're not sure whether apparent power (kVA) is (kW x pf) or (kW / pf), then try both... the one where you get a higher number is the correct one.

pf = kW / kVA <---- FACT

So kVA = kW / pf = 7.5 / 0.9 = 8.33kVA

So the current flowing is 8333 / 230 = 36.23A.

So it's the answers in the mock exam paper that are all wrong.

The correct answer is: "none of the above"

Where is the mock paper from, out of interest? Wouldn't be the first time someone's made an error in an exam paper...

I pmed hightower to avoid confusion and I'm glad someone has reached the same conclusion as me ,

 

[hightower]

Steve, you're here again and saving my brain. I was 99% sure I was right with 36.23A but doubt was starting to creep in. Thank you for confirming it, my mind can now disengage and I can hopefully get rid of this headache.

The paper is from SmartScreen and created by C&G - it's not a past paper I don't think, just a mock paper. It's entitled:

202: Principles of electrical science Sample Questions

 

[happysteve]

It's irritating, isn't it, when the very people who are supposed to be helping you learn stuff end up confusing you due to careless mistakes on their part?

There are all kinds of errors on the SmartScreen material, particularly the powerpoint slides.

I suggest you mention this question to your tutor, so that he/she can point it out to the other learners, to avoid even more headaches!

 

[hightower]

It's irritating, isn't it, when the very people who are supposed to be helping you learn stuff end up confusing you due to careless mistakes on their part?

There are all kinds of errors on the SmartScreen material, particularly the powerpoint slides.

I suggest you mention this question to your tutor, so that he/she can point it out to the other learners, to avoid even more headaches!

Ah, me and Pete have had a good bit banter via PM trying to get to the bottom of it.

We're going to be going through the mock paper on Monday, but it was really bothering me hence asking here. As sad as it is, I really wouldn't have slept tonight until my mind was put at rest.

I noticed 3 errors in the 2365 L2 textbook in the first 20 or so pages of the 202 material - simple maths errors, and one on trigonometry where:

TOH
CAH
SOH

Where it should have read

TOH
CAH
SOA

 

[happysteve]

I noticed 3 errors in the 2365 L2 textbook in the first 20 or so pages of the 202 material - simple maths errors, and one on trigonometry where:

TOH
CAH
SOH

Where it should have read

TOH
CAH
SOA

You sure about that?

There is summat wrong with the text book version, but it's not the "SOH" that's the problem...

 

[hightower]

You sure about that?

There is summat wrong with the text book version, but it's not the "SOH" that's the problem...

Yeah, sorry

It's

SOH CAH TOA

but in the book it's

SOH CAH TOH as far as I can remember,

 

[Pete999]

Well don't know about anyone else, but for me even at my stage in life gives a good example to all the younger members who are still taking exams etc, is to read the question properly, and don't rush into making rash assumptions, as I did, got there in the end though.

:wheelchair:

 

[Simonslimline]

Excellent, so i am not going mad then. Thanks Steve. :rockon2:

 

[hightower]

Excellent, so i am not going mad then. Thanks Steve. :rockon2:

My sentiments exactly.

 

[Simonslimline]

Just to add, i have had lots of dodgy practise papers in the past with wrong answers etc. Even when i took the 309 science and principles exams C&G got on of the questions wrong in the paper. I had to argue my case and prove my answer to my tutor for the marks.

It was regarding a star connected TPN system 120 degrees apart and unbalanced across the 3 phases.

 

[Simonslimline]

I think City & Guilds forgot the laws of physics for a minute.