Energy Dissipated

[skystorm]

Hi all

Here is one, A current of 4.5A flows in a 3.5ohms resister for 5.5 minutes. The energy dissipated is ,

can anyone refesh this old mind of my and show how its done thanks

 

[davetheglitz]

Power (Watts) = I(Ampere) squared . R(ohm)

Energy (Joule) = Power(Watts) . Time (second)

 

[johninlondon1]

4.5 squared x 3.5 x 330 = 23,388.75 Joules, or 23.38875 KJ

 

[skystorm]

I get 2,450,12

 

[skystorm]

4.5 x 3.5 x 330 =2,450,12 missed the squared out , if i do it with the square in i get syntax error

 

[m4tty]

You must be pressing wrong sequence on calculator mate. Do 4.5 squared first by doing 4.5 x 4.5 then press equals then do rest of sum.

 

[skystorm]

Thanks all need to get a new calculator been a long day

 

[steptoe]

well whaddya know,

never ever seen a calculator returning a syntax error before.!!! :C

you sure you have 2391?

we werent even allowed scientific calculators when I done mine.

 

[steptoe]

My HP will return a syntax error, but it's old and a proper calculator RPN and all that - whatever that means!

scientific?

 

[SPECIAL LOCATION]

well whaddya know,never ever seen a calculator returning a syntax error before.!!! :C

you sure you have 2391?

we werent even allowed scientific calculators when I done mine.

Thats cuz they weren't invented!!!!!!

Slide-rule...

Pencil...

& back-o-the-fag-packet you told Deke????

 

[steptoe]

and a

i89f54j to you too!

 

[apprentice87]

Hi All,

I will do it the "pen and paper way" or just using the extremely basic calculator on my PC and my not very up to speed brain!!!

Right, so we have a resistor of 3.5 ohms and a current of 4.5 Amps..

So, current times resistance gives voltage, so 3.5 ohms x 4.5 Amps = 15.75 Volts..

Now, Volts times current gives Watts.. So, 15.75 Volts x 4.5 Amps = 70.875 Watts.

Now, this "power", i suppose is the best term, [the 70 odd watts] is flowing for 5.5 minutes.

5.5 minutes is obviously 5.5 x 60 seconds = 330 seconds

A Watt flowing for one second = one Joule...

So if we multiply our 70.875 Watts by 330 seconds, we come up with 23388.75 Joules which is the answer!!

So, energy dissipated... 23388.75 Joules

john..