-
A plastic sleeve of outer radius r0 = 1 mm covers a wire (radius r = 0.5 mm) carrying electric current, Thermal conductivity of the plastic is 0.12 W/mK. The heat transfer coefficient on the outer surface of the sleeve exposed to air is 25 W/m2K. Due to the addition of the plastic cover, the heat transfer from the wire to the ambient will
-
- increase
- remain the same
- decrease
- be zero
Correct Option: A
r0 = 1 mm, k = 0.15 W/m-k
h = 25 W/m2 -K
| rc = | for cylindrical shape | h0 |
| = | × 1000 = 0.15 × 40 = 6mm | 25 |
∴ rc > r0
⇒ The heat transfer from the wire to the ambient will increase
