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.

roughly 6kwh

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.

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

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


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

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.    

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.

Quote:


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.