Answer:
Step-by-step explanation:
The heat dissipated or loss at the top of the surface is given by
Qloss = -KA ∆T
Qloss = -KA (Ts - Ta)
Where
K is thermal conductivity of material
A is the cross-sectional area
L is the thickness or length of material
Ta is the temperature of air.
Ts is the temperature at the surface
Ts–Ta is the difference between skin temperature and air temperature.
Given that,
Temperature of air Ta=20°C
Plate dimensions are 50cm by 40cm
Converting to metre = 0.5m by 0.4m
Area = length × breadth
Area=0.5×0.4
Area=0.2m²
The temperature at surface
Ts=40°C
Let assume an aluminium plate then, k = 0.0263 W/m⋅K,
We don't need to convert the temperature to Kelvin, since we are going to use the change in temp.
Applying the formulas
Qloss = -KA (Ts - Ta)
Qloss = - 0.0263 × 0.2 × (40-20)
Qloss= -0.0263 × 0.2 × 20
Qloss= -0.1052J
The heat loss is 0.1052J