JAMB - Physics (2003 - No. 22)
If 1.2 x 10^6J of heat energy is given off in 1 sec from a vessel maintained at a temperature gradient of 30Km-1, the surface area of the vessel is
[ thermal conductivity of the vessel = 400Wm-1K-1]
1.0 x 102m2
9. 0 x 102m2
1.0 x 103m2
9.0 x 104m2
Explanation
Generally in thermal/heat conduction, if 1.2 x 106 J is the heat flow per seconds; 30KM-1 is the temperature gradient of the materials; and 400Wm-1K-1 the thermal conductivity of the material, then we have that:
heat energy = thermal conductivity x temp. gradient x time x area
i.e = 1.2 x 10^6
= 400 x 30 x1x Area
=> 400 x 30 x Area = 1.2 x 10^6
∴ Area = (1.2 x 10^6)/(400 x 30)
Area = 100m^2 or 1.0 x 10^2m2
heat energy = thermal conductivity x temp. gradient x time x area
i.e = 1.2 x 10^6
= 400 x 30 x1x Area
=> 400 x 30 x Area = 1.2 x 10^6
∴ Area = (1.2 x 10^6)/(400 x 30)
Area = 100m^2 or 1.0 x 10^2m2
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