How long will it take to boil 1 liter of water?

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SUMMARY

The discussion centers on calculating the time required to boil 1 liter of water from 20°C to 100°C using a kettle with an efficiency of 85%, a voltage of 230V, and a power rating of 200W. The energy required for this process is calculated as 334,400 joules. Participants confirm the energy calculation is correct and emphasize the need to apply the kettle's power and efficiency to determine the boiling time. The key formula involves converting power into time using the relationship that 1 watt equals 1 joule per second.

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  • Understanding of thermodynamics, specifically heat transfer and energy calculations.
  • Familiarity with the concept of power in watts and its relation to energy in joules.
  • Basic knowledge of efficiency calculations in energy systems.
  • Ability to manipulate equations to solve for time using power and energy.
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  • Learn how to calculate time from energy and power using the formula: time = energy / (power * efficiency).
  • Explore the concept of thermal efficiency in heating systems and its impact on energy consumption.
  • Study the relationship between joules, watts, and seconds for practical applications in physics.
  • Investigate other methods of boiling water and their efficiencies, such as induction vs. electric kettles.
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EMEE_
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Homework Statement
How long will it take to boil 1 liter of water from 20°C? The heat efficiency / η is 85% , voltage / U 230V and power / P 200W. The answer must be given in seconds.
Relevant Equations
?
Hi.
I have been trying to solve the following problem:How long will it take to boil 1 liter of water from 20°C? The heat efficiency / η is 85% , voltage / U 230V and power / P 200W. The answer must be given in seconds.

So,

t1 = 20°C

t2 = 100°C

Δt = 80°C

V = 1,0 liter → m = 1,0 kg

ηkettle = 85%

U = 230V

P(the power needed to boil water) = 200W

So far I have solved the energy consumed in boiling water: E = c * m * ∆t = 334400_J (joules) Have I used the right formula? And what formulas can I use?

Hopefully, someone here can help me!
 
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Are you just supposed to bring it to a boil (begin boiling) or boil it all away?
 
I'm just supposed to bring it to a boil.

phyzguy said:
Are you just supposed to bring it to a boil (begin boiling) or boil it all away?
 
EMEE_ said:
I'm just supposed to bring it to a boil.
Then your calculation of the energy required looks correct. Do you know how to go from there to the time required? You will need to use the input power and efficiency.
 
phyzguy said:
Then your calculation of the energy required looks correct. Do you know how to go from there to the time required? You will need to use the input power and efficiency.

Ok, good if the calculation is correct! :). But I don't actually know how to go from there to the time required...
 
Hi EMEE:

Does it help to know that a watt is a joule per second?

Regards,
Buzz
 
Buzz Bloom said:
Hi EMEE:

Does it help to know that a watt is a joule per second?

Regards,
Buzz

Yeah, thanks, that might help. But I don't really know what formulas/ equations I should use... Could you please help with those?
 
If I'm going 50 miles per hour, and I have 300 miles to travel, how long will it take? If I'm putting in 200 Joules per second, and I need 334400 Joules, how long will it take?
 

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