Electric immersion water heater time

AI Thread Summary
An electric immersion water heater rated at 400 W is tasked with heating one liter of water from 10°C to 30°C. The specific heat of water is 1 cal/g*K, and the mass of one liter of water is 1000 grams. To determine the time required for heating, one must calculate the total heat needed using the calorimetric equation, which relates mass, specific heat, and temperature change. The confusion arises from understanding the connection between watts, joules, and the mass of water. The correct approach involves recognizing that 1 liter of water equals 1000 grams, and using the power rating to find the time needed to supply the required heat.
rgold
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Homework Statement


The mechanical equivalent of heat is 1cal=4.18J. The specific heat of water is 1cal/g*K and its mass is 1g/cm^3. an electric immersion water heater rated at 400 W should heat a liter of water from 10C to 30C in about how much time

Homework Equations


R=v/i
power=v*i

The Attempt at a Solution


I know the answer is 3.5 minutes but i do not know how to get there. I am pretty lost.[/B]
 
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rgold said:

Homework Statement


The mechanical equivalent of heat is 1cal=4.18J. The specific heat of water is 1cal/g*K and its mass is 1g/cm^3. an electric immersion water heater rated at 400 W should heat a liter of water from 10C to 30C in about how much time

Homework Equations


R=v/i
power=v*i

The Attempt at a Solution


I know the answer is 3.5 minutes but i do not know how to get there. I am pretty lost.[/B]
Work out the units. What is a watt? How many grams of water are in 1 liter?

BTW, the formulas in Section 2 won't help you with this problem, since you don't know voltage, current, or resistance.
 
SteamKing said:
Work out the units. What is a watt? How many grams of water are in 1 liter?

BTW, the formulas in Section 2 won't help you with this problem, since you don't know voltage, current, or resistance.

im still confused i know that a watt is joules per second and that 1000 grams of water in a liter but how do i connect everything?
 
Last edited:
rgold said:
The mechanical equivalent of heat is 1cal=4.18J. The specific heat of water is 1cal/g*K and its mass is 1g/cm^3. an electric immersion water heater rated at 400 W should heat a liter of water from 10C to 30C in about how much time

Homework Equations


R=v/i
power=v*i
you should calculate amount of heat required to raise the water from t1 to t2 given -then calculate the time taken by the heater to provide that heat-
heat req.= related to( massxsp. heatx temp diff ) by calorimetric equation
 
rgold said:
im still confused i know that a watt is joules per second and that 100 grams of water in a liter but how do i connect everything?

You need to go back and study the SI system some more. 1 liter contains way more than 100 grams of water.
 
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