- #1

Stavrosnt

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## Homework Statement

Hi, as a part of my lab report I have to conduct this experiment : Fill a pot with tap water and boil it, determine then how much of the energy that the kitchen surface produced, actually went to the water itself. Consider the water having an initial temperature of 10 °C. In order to conduct the experiment I used an induction surface cook top. I filled a pot with 1litre of tap water and recorded the time it took to boil, which was 163 seconds. I then found out the power output of my cooking surface online which is 1.9 kW.

## Homework Equations

E thermal = c *m* (ΔT)

c = materials thermal constant , which for water is 4.18 kJ/kg°C (constant given by my book)

ΔT= Difference in temperature

P= E/t (Watt formula)

## The Attempt at a Solution

First, I tried to find the energy produced by my surface during the time it took to boil the water:

P=E/t , E=P*t , E= ( 1.9*10^3 W)* (163 s) = 309 700J .

Then I tried to find the energy needed to turn a 1 liter of water from 10°C to 100°C. 1 liter of water has a mass of 1 kg

E = c*m* ΔT = (4.18 * 10^3 ) * (1kg) * (100-10)= 376 200 j

The energy expended by the cooking surface should not be smaller than the energy needed to cook the water. Where have I made my mistake?

Sadly, i don't have access to a thermometer in order to measure the exact temperature of the water coming out of the tap. Also, I am using an induction surface to cook the water. Could it be that I am using a wrong formula in my calculations due to the fact that induction surfaces use electromagnetism in order to heat the pot directly?

Do you have any ideas?