Currect flowing in a circuit & Heater resistance questions

[Ed work]

Hello everyone i am new to the forum.

I am revising for my exams and have come across two questions that i don't know the equation to.

1. A single-phase circuit dissipates 2.5kw of power and operates at a power factor of 0.95. The current flowing in the circuit will be:

a/. 11.4 A

b/. 10.32 A

c/. 10.8 A

d/. 10.4 A

2. An electric heater dissipates a power of 3.0kw when connected to a 230V a.c supply. The resistance of the heater is:

a/. 13.0 ohms

b/. 15.65 ohms

c/. 17.6 ohms

d/.35.2 ohms

Could you show me the equations and workings out to?

Thanks.

Ed.

 

[Andy™]

Q1. you havent said voltage, but assuming 230V

KW / PF = KVA

2.5 / 0.95 = 2.63Kva

2630 / 230 = ....

Q2: [removed - see post below]

you can fill in answers

 

[sarni31]

Q1. you havent said voltage, but assuming 230VKW / PF = KVA

2.5 / 0.95 = 2.63Kva

2630 / 230 = ....

Q2: 3000 / 230 = .....

you can fill in answers

Q2 Need to work out the current first

AMPERES = POWER / VOLTS

3KW(3000) / 230V = 13A

Then for the resistance

RES = VOLTS / AMPERES

230V / 13A = 17.6ohm

 

[Andy™]

Q2 Need to work out the current firstAMPERES = POWER / VOLTS

3KW(3000) / 230V = 13A

Then for the resistance

RES = VOLTS / AMPERES

230V / 13A = 17.6ohm

your right. for some reason i worked out amps instead of ohms

 

[PoorFish]

Hi folks

please correct me if this is wrong but could the formula for question 1 be

I = P/V x PF

I = 2500/230 x .95

I = 10.32 Amps

is there a difference in formulas when we have "the power dissapated" or when "power is consumed"

Pat

 

[sarni31]

I used the same formula so got 10.32A as well..

Guiness Drink

 

[bobby]

Is this 2330 level 2 unit 3 stuff? never seen these type of questions before, I have somthing similar but with a totally different formula which dont work for these questions. ?:|

 

[PoorFish]

as far as i know it is ....

but I wouldnt have a clue on the likelyhood of being asked anything about this in the exam.

 

[Andy™]

id say the less you know of a specific formula, the greater the chance of there being a question on it...

 

[steptoe]

id say the less you know of a specific formula, the greater the chance of there being a question on it...

how very true.

by the way,

Im not allowed to answer these type of questions cos my answers are usually totally useless to being the correct methods and/or equasions, albeit with the same answers my methology(?) is somewhat lacking.

 

[a1]

These are Level three questions - I have the same ones on a mock paper too.

I think AndyC is correct in Post #2

And

I think Sarni is correct in post #3.

 

[a1]

As you know Guys:

I have put together a webpage of Electrical Formulas (Formulaes) or equations.

It's hectic at present with exams and Assignments to do before completing my Level 3 in June.

I would appreciate if you guys have time... If you could E-mail me whatever formulas you can think of, including symbols and units etc.

I will get round to doing it, but, as I say - would appreciate if some of you could help, if possible please?

Regards,

Admin.

 

[Jono Pashley]

Know how you feel Admin, i have 2 exams and an Assignment within the space of a month, got a month to cover all of 205 ready for exam..

 

[Andy™]

so much easier once your qualified....then you just have to go through yearly assessments if you want to be part of a scam

 

[a1]

Indeed Gents.

I have my 301 (last of the online multi choice) this Wednesday. - Not looking forward to that.

I have my 302 Inspection and testing Assignment to do, Tomorrow or a week Tomorrow.

I have my 303 Fault Finding Assingment to do.

And

302 Written Exam

303 Written Exam.

:_| :_| :_|

 

[Andy™]

Enjoy!

 

[batty]

Indeed Gents.I have my 301 (last of the online multi choice) this Wednesday. - Not looking forward to that.

I have my 302 Inspection and testing Assignment to do, Tomorrow or a week Tomorrow.

I have my 303 Fault Finding Assingment to do.

And

302 Written Exam

303 Written Exam.

:_| :_| :_|

Crumbs you are going to be busy Mr Admin.

Batty

 

[bobby]

These are Level three questions - I have the same ones on a mock paper too.I think AndyC is correct in Post #2

And

I think Sarni is correct in post #3.

A relief to see its level 3 bit late in the game for me to get my head round these formulas being my 203 online test tommorow

 

[searley]

got my 301 coming up if you remember any questions will you post them on here cheers.

 

[a1]

A relief to see its level 3 bit late in the game for me to get my head round these formulas being my 203 online test tommorow

So Much to do and so little time to do it in - I am Nervous. :_|

The college are changing the 2330 from a two year course to a three year course form September.