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

[EMEE_]

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

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Hi.
I have been trying to solve the following problemow 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!

 

[phyzguy]

Are you just supposed to bring it to a boil (begin boiling) or boil it all away?

 

[EMEE_]

I'm just supposed to bring it to a boil.

Are you just supposed to bring it to a boil (begin boiling) or boil it all away?

 

[phyzguy]

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.

 

[EMEE_]

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...

 

[Buzz Bloom]

Hi EMEE:

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

Regards,
Buzz

 

[EMEE_]

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?

 

[phyzguy]

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?