The heat absorbed by a 2.4 m\(^2\) of a brick oven whose temperature gradient is 400 K m\(^{−1}\) in 2 hours is [k = 0.85 W m\(^{−1}\)K\(^{−1}\)]
A
0.3MJ
B
5.9MJ
C
3.2MJ
D
7.6MJ
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
Rate of heat flow (conduction) is given by: \(\frac{\text{Q}}{\text{t}}\) = kA\(\frac{\Delta θ}{\Delta x}\)
\(\frac{\text{Q}}{\text{t}}\) = 0.85 × 2.4 × 400 = 816W = 816Js\(^{−1}\)
Time = 2 hours = 2 × 3600 =7200 secs
Q = 816 × 7200 = 5 875 200 J ≈ 5.9 MJ
Source: WAEC / JAMB / NECO Classroom Archive (Record #78262)