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Topic Title: What is the formula?
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Created On: 20 April 2013 03:37 PM
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 20 April 2013 03:37 PM
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harper1993

Posts: 3
Joined: 02 April 2013

Can someone please help me out and give me the formula for this question, I have my C&G level 3 301 exam coming up in 3 weeks and im undertaking 5 hours revision a day. I did this kind of question at the start of the year but I have forgot the formula and cant find it anywhere..

A single phase circuit dissipates 2.5 kW of power and operates at a power factor of 0.95. The current flowing will be :

A. 11.4A
B. 10.32A
C. 10.8A
D.10.4A
 21 April 2013 01:40 PM
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benmc

Posts: 26
Joined: 02 November 2012

I = P/V

I=2500/230

I= 10.86

i dont think you need to worry about the powerfactor too much as its 0.95 but i may be wrong,
 21 April 2013 02:23 PM
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westonpa

Posts: 1771
Joined: 10 October 2007

At which voltage?
 21 April 2013 05:58 PM
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dazzjones

Posts: 16
Joined: 12 July 2009

Hi harper,

Assuming that the single phase voltage is 230V....

I = P / (V × cos φ)

Power factor PF = cos φ

Therefore...

I = 2500w / (230 x 0.95)

I = 2500 / 218.5

I = 11.44A

Correct answer = A


Hope this helps,
Kind regards,
Darren
 02 June 2013 11:15 PM
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l30f1tz

Posts: 2
Joined: 02 June 2013

Originally posted by: dazzjones

Hi harper,



Assuming that the single phase voltage is 230V....



I = P / (V × cos φ)



Power factor PF = cos φ



Therefore...



I = 2500w / (230 x 0.95)



I = 2500 / 218.5



I = 11.44A



Correct answer = A





Hope this helps,

Kind regards,

Darren


+1 What Darren has said. If the voltage was not given and it stated single phase, then one can only assume its a 230V supply.
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