Question

You are boiling pasta and absentmindedly grab a copper stirring spoon rather than your wooden spoon. The copper spoon has a 20 mm × 1.5 mm rectangular cross section, and the distance from the boiling water to your 35∘C hand is 18 cm. How long does it take the spoon to transfer 40 J of energy to your hand?

Answer 1

The spoon to transfer 40 J of energy to your hand is descibed as follows

Explanation:

Given  area of cross section of copper spoon is A = 20mm into 1.5 mm

temperature difference is DT = (100 minus 35) = 65 0C

length of the spoon is l = 18 cm,

amount of heat should be transfer Q = 40 J

coefficient of thermal conductivity of copper k = 400 W by mk

we know that the thermal conductivity is Q by t = k into A into DT by l

t = Q into l by k into A into DT

t = (40 into 0.18) by  $\left(400 \times 30 \times 10^{-6} \times 65\right)$

t = 9.23 s