Find the time needed to warm the water to a temperature

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Homework Help Overview

The discussion revolves around calculating the time required to heat 10 liters of water from 20°C to 120°C using an electrical resistance with a power output of 1 kW. The context involves thermodynamics and energy transfer principles.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between power, time, and energy, questioning the definitions and dimensions of the symbols used. There is an exploration of the energy required to heat the water and the implications of the container's conditions.

Discussion Status

Participants are actively engaging with the problem, seeking clarification on the equations and assumptions involved. Some guidance has been offered regarding the need to define terms and consider the energy required for heating the water.

Contextual Notes

There is uncertainty regarding the container's configuration (open or closed) and how it affects the heating process, particularly at higher temperatures. The original poster has made corrections to their notation but further clarification is still sought.

MaiteB
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Homework Statement


An electrical resistance has a power of 1 kW. It is put inside a container that has 10 liters water. The water is in temperature 20C with pressure 1 atm. Find the time to warm the water to the temperature 120C

Homework Equations


A=P*t

The Attempt at a Solution


I thought to use the equation p1/T1=p2/T2 and t=P/A. How can i find A?
 
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Hello MB,

Well, if A is P*t, then writing t = P/A seems a little strange !

So perhaps you can shed a little light here ? First of all, what are these symbols representing ? And their dimensions ?

Warming up water takes heat, energy. The more energy per unit of time (a.k.a. power), the faster it goes.

Furthermore, they tell you the 10 liters of water are at a temperature of 20 ##^\circ##C in a container at a pressure of 1 atm. They don't tell you if the container is closed and kept at a constant volume, or if it's open. In other words, what happens at a temperature of, say, 100 ##^\circ##C :rolleyes: ?

[edit]Oh, and your thread will soon be moved to the introductory physics section by the good spirits that watch over PF
-
 
Last edited:
MaiteB said:

Homework Statement


An electrical resistance has a power of 1 kW. It is put inside a container that has 10 liters water. The water is in temperature 20C with pressure 1 atm. Find the time to warm the water to the temperature 120C

Homework Equations


A=P*t

The Attempt at a Solution


I thought to use the equation p1/T1=p2/T2 and t=A/P. How can i find A?
I corrected it. t-time, A-work, P-power
 
Good (although I don't see it anywhere).
What about the p1T1 = p2T2 ? what are they ?
Can you write an equation to calculate how much energy is needed to heat up 10 liters of water by one degree C ?
 

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