Amount of kWh used to heat water

  • Thread starter rullervea
  • Start date
  • #1
1
0

Homework Statement



How much kWh is beeing used to heat 285 liters of water in a water heater from:
1. + 5 °C to + 75 °C
2. + 20 °C to + 75 °C

Homework Equations



Found this equation:

kWh = (Q*CJ*∆t)/T

The Attempt at a Solution



Q = liter = 285
Cj = heat capacity = 4,18
∆t = 70 for 1. And 55 for 2.
T = is the time, but I'm not sure what to use here, so I used 3600.

So my answer was:
1. 23,2 kWh
2. 18,2 kWh

I have no clue if this is right or wrong because of the variable T. What is correct here?
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
6,223
31
kWh is a unit of energy, so just calculate the energy using QC∆t, and then convert.

1 kWh = 1 kW * 1 hr = 1000 J/s * 3600 s = 3,600,000 J

So 1 J is?

Then just convert!
 

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