FYKOS Year 32 Series 3 Problem 2 — efficient coffee · FYKOS 32 #32.3.2

Physics · mechanics · thermodynamics

Problem

It is 2 am and Jáchym is going to make a coffee. He places a kettle with the heat capacity of

C_k

on a hot plate, which is made of a cast-iron cylinder of a radius

r

and of height

h

. The kettle contains water with a volume of

V

with an initial temperature of

T\_v

. The rest of the system has got an initial temperature of

T\_s

. What is the overall efficiency (ratio of energy absorbed by water vs energy input) of water heating from its initial temperature

T = 100 \mathrm{\C }

(T\_s, T\_v < T).

Assume, that the heat transfer is very fast and therefore there is no heat loss. You can estimate the unknown values or find them in physics tables.