Ask The Trades - Print Page

Ask The Trades
https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> Electrical Question https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1240513059 Message started by col on Apr 23^rd, 2009, 7:57pm

Title: Electrical Question
Post by col on Apr 23^rd, 2009, 7:57pm

I've been asked ? if 13A flows for 2 hours in a circuit, what is the quantity of electricity that has passed ?
I think I am looking too deep into the answer by finding out the price per kilowatt etc. Does anyone know and can briefly explain the answer ? Thanks Very Much, Col.

Title: Re: Electrical Question
Post by londonman on Apr 23^rd, 2009, 9:15pm

Sounds like one for Chubby to answer.

Title: Re: Electrical Question
Post by scotspark on Apr 23^rd, 2009, 9:24pm

roughly 6kwh

Title: Re: Electrical Question
Post by ChubbyPhaseWire on Apr 23^rd, 2009, 10:28pm

londonman wrote on Apr 23^rd, 2009, 9:15pm:

Sounds like one for Chubby to answer.

;)

Title: Re: Electrical Question
Post by Y3 on Apr 23^rd, 2009, 11:06pm

230v x 13a = 2,990w per hour,

2,990 x 2 hours = 5,980w

If your charged 10p per kWh, then thats about 60p in total.

In physics the term quantity of electricity refers to the quantity of electric charge. It is designated by the letter Q and in the SI system is measured in derived units called coulombs.

Title: Re: Electrical Question
Post by Twobarrows on Apr 24^th, 2009, 12:00am

wrote on Apr 23^rd, 2009, 10:28pm:

londonman wrote on Apr 23^rd, 2009, 9:15pm:

Sounds like one for Chubby to answer.

;)

I don't think Fatty knows the answer.

Title: Re: Electrical Question
Post by Twobarrows on Apr 24^th, 2009, 12:01am

1A = 1 C /s, so it's 3600x13x2 = 93600C

Title: Re: Electrical Question
Post by CWatters on Apr 24^th, 2009, 9:25am

Now that and this might confuse him :)

C= Coulomb = the SI unit for electrical charge...

http://en.wikipedia.org/wiki/Coulomb

Y3's answer gets my vote.

Title: Re: Electrical Question
Post by Twobarrows on Apr 24^th, 2009, 2:28pm

CWatters wrote on Apr 24^th, 2009, 9:25am:

Now that and this might confuse him :)

Y3's answer gets my vote.

Ah, but his answer was 5,980w, which doesn't answer the question, plus it makes assumptions.

Title: Re: Electrical Question
Post by CWatters on Apr 24^th, 2009, 5:31pm

Ah yes I see he assumed 230V.

Title: Re: Electrical Question
Post by Y3 on Apr 24^th, 2009, 6:03pm

He wanted to know the price per kWh, so thats where my calculation came from. I liked chubbs answer though, not done that stuff since college. I make that sound like it was ages ago, but its not. ;D

Title: Re: Electrical Question
Post by Twobarrows on Apr 27^th, 2009, 8:46am

wrote on Apr 24^th, 2009, 6:03pm:

He wanted to know the price per kWh, so thats where my calculation came from. I liked chubbs answer though, not done that stuff since college. I make that sound like it was ages ago, but its not. ;D

Nope, here's the question, 'I've been asked ? if 13A flows for 2 hours in a circuit, what is the quantity of electricity that has passed ?'
No mention of price there, no mention of voltage either!

Title: Re: Electrical Question
Post by TibbarTibbar on Apr 27^th, 2009, 7:41pm

To answer the question more information is needed 2barrows....

1. What is the load resistive, capacitive or inductive?

2. Any corrective circuit components installed (if inductive/capacitive)?

3. Calcs will normally be done assuming 230 volts if you want an actual average to be used please provided applicable data from an installed data logger.

Nothing can be derived from the statement 13A for 2 hours.

Title: Re: Electrical Question
Post by Y3 on Apr 27^th, 2009, 8:12pm

wrote on Apr 23^rd, 2009, 7:57pm:

I think I am looking too deep into the answer by finding out the price per kilowatt etc. Does anyone know and can briefly explain the answer ? Thanks Very Much, Col.

YES Twobarrows.....

As above

Title: Re: Electrical Question
Post by Twobarrows on Apr 28^th, 2009, 4:03pm

wrote on Apr 27^th, 2009, 7:41pm:

To answer the question more information is needed 2barrows....

3. Calcs will normally be done assuming 230 volts if you want an actual average to be used please provided applicable data from an installed data logger.

Nothing can be derived from the statement 13A for 2 hours.

Actually, you don't need to know the voltage as the current is stated, and current is simply the flow, so the answer can easily be derived and given in either Coulombs or absolute # of electrons if you really want.

It can be a bit confusing if you are not used to soving problems from first pricipals, in this case people tend to make it more complicated than it actually is. To use the ever popular water analogy, if you know the flow rate (current) and time you know how much water has passed, the pressure (voltage) is immaterial.

Assuming 230v would be an error in many cases, as it isn't :-)

Interesting question though.