A 10 mm diameter electrical conductor is covered by an insulation of 2...
rc = 8mm
∴ the heat lost increases to maximum and then decreases.
View all questions of this test
A 10 mm diameter electrical conductor is covered by an insulation of 2...
Explanation:
1. Heat Loss Calculation:
To understand why the heat loss will initially increase and then decrease, we need to calculate the heat loss through the conductor before and after the addition of the insulation.
Heat loss through the conductor:
The heat loss through the conductor can be calculated using the formula:
Q = (k * A * ΔT) / L
Where:
Q = Heat loss (W)
k = Thermal conductivity of the conductor (W/mK)
A = Cross-sectional area of the conductor (m^2)
ΔT = Temperature difference between the inner and outer surfaces of the conductor (K)
L = Length of the conductor (m)
Assuming the temperature difference ΔT remains constant, the heat loss through the conductor can be simplified as:
Q = (k * A) / L
2. Heat Transfer Calculation:
Heat transfer through the insulation:
The heat transfer through the insulation can be calculated using the formula:
Q = (k * A * ΔT) / L
Where:
Q = Heat transfer (W)
k = Thermal conductivity of the insulation (W/mK)
A = Surface area of the insulation (m^2)
ΔT = Temperature difference between the inner and outer surfaces of the insulation (K)
L = Thickness of the insulation (m)
Assuming the temperature difference ΔT remains constant, the heat transfer through the insulation can be simplified as:
Q = (k * A) / L
3. Analysis:
Initially, the heat loss through the conductor is given by Q = (k * A) / L. When the insulation is added, the heat transfer through the insulation can be calculated using Q = (k * A) / L. Since the insulation thickness is 2 mm, the new thickness of the combined insulation is 4 mm.
When additional insulation of the same material is added, the total thickness of the insulation increases. As a result, the heat transfer through the insulation decreases because the insulation thickness in the formula is in the denominator.
However, the heat loss through the conductor remains the same since the conductor's cross-sectional area and length do not change.
Initially, the heat loss is predominantly through the conductor, and the added insulation reduces the heat loss through the insulation. But as more insulation is added, the heat loss through the conductor becomes relatively smaller compared to the heat loss through the insulation. Therefore, the heat loss initially increases as the insulation thickness increases.
Eventually, there will be a point where the heat loss through the insulation becomes significant enough that further adding insulation will not significantly affect the overall heat loss. At this point, the heat loss reaches a maximum and starts decreasing as the additional insulation further reduces the heat transfer through the insulation.
4. Conclusion:
Hence, the correct answer is option C: the heat loss will increase to a maximum and then decrease as further insulation of the same material is added.
A 10 mm diameter electrical conductor is covered by an insulation of 2...
rc = 8mm
∴ the heat lost increases to maximum and then decreases.
To make sure you are not studying endlessly, EduRev has designed Mechanical Engineering study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in Mechanical Engineering.