Answer in Physics for Mike #226543

Here’s what I believe the complete condition of the problem is:

An electric immersion heater has a power rating of 1500 W. If the heater is placed in a liter of water at 20°C, how many minutes will it take to bring the water to a boil? (Assume that there is no heat loss except to the water itself.)

So, the energy required to increase the temperature is

“Q=cmDelta tau.”

The electrical energy required for this is equivalent to power times time:

“E=Pt,\nQ=E,\ncmDeltatau=Pt,\space\nt=frac{cmDeltatau}{P}=frac{4200u00b71u00b7(100-20)}{1500}=224text{ s},”

or 3 min 44 s.