A) 0.6 W
B) 0.9 W
C) 1.6 W
D) 1.8 W
Correct Answer: C
Solution :
| [c] Let R = total thermal resistance of the ring, \[\Delta T=\] difference in temperature between A and B. For \[\theta ={{180}^{o}},\] two sections of resistance R/2 each are in parallel. |
| Equivalent resistance \[=\frac{R}{4}\]. |
| Rate of total heat flow \[={{I}_{1}}=1.2=\frac{\Delta T}{r/4}\] |
| Or \[0.3=\frac{\Delta T}{R}\] |
| For \[\theta ={{90}^{o}}\] two sections of resistances \[\frac{R}{4}\] and \[\frac{3R}{4}\] are in parallel. |
| Equivalent resistance \[=\frac{(R/4)(3R/4)}{R/4+3R/4}=\frac{3R}{16}\] |
| Rate of total heat flow \[{{I}_{2}}=\frac{\Delta T}{3R/16}W=\frac{16}{3}\left( \frac{\Delta T}{R} \right)W=\frac{16}{3}\times 0.3W=1.6W\] |
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