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# 11.2 specific heat capacity watch

1. Really stuck on a summary question in my physics book

An electric shower is capable of heating water from 10 degree celsius to 40 degree celsius when the flow rate is at 0.025kg/s. calculate the minimum power of the heater.

2. I get the correct answer in the back of the book by doing the calculation P = 30 x 4200 x 0.0.25 where 4200 = specific heat capacity of water but i don't see why
3. The specific heat capacity of water is 4200J/kg degrees Celsius. The change in temperature from 10 degrees Celsius to 40 degrees Celsius is 30 degrees Celsius. To work out the minimum power of something, it is the specific heat capacity of the substance it is heating multiplied by the temperature change multiplied by the flow rate I believe.
4. (Original post by LogicalFallacy)
The specific heat capacity of water is 4200J/kg degrees Celsius. The change in temperature from 10 degrees Celsius to 40 degrees Celsius is 30 degrees Celsius. To work out the minimum power of something, it is the specific heat capacity of the substance it is heating multiplied by the temperature change multiplied by the flow rate I believe.
Thank you, I don;t think i have came across that equation before.
5. (Original post by gerrard1998)
Thank you, I don;t think i have came across that equation before.
I hope I helped!
6. (Original post by gerrard1998)
Thank you, I don;t think i have came across that equation before.
it's testing whether you are able to adapt the SHC formula.

The key is that power is Joules per second
and
flow is kg per second

so in each second you have a known mass of water going through the showers element... and all of that water is heated up by a known ΔT

work out the amount of energy in Joules needed to heat up one seconds worth of water and the answer is the power in Watts.
7. (Original post by Joinedup)
it's testing whether you are able to adapt the SHC formula.

The key is that power is Joules per second
and
flow is kg per second

so in each second you have a known mass of water going through the showers element... and all of that water is heated up by a known ΔT

work out the amount of energy in Joules needed to heat up one seconds worth of water and the answer is the power in Watts.
Thank you

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