Question

A and B are two points on a uniform metal ring whose centre is C. The angle ACB = q. A and B are maintained at two different constant temperatures. When q = 180ŗ, the rate of total heat flow from A to B is 1.2 W. When q = 90ŗ, this rate will be –

• A. 0.6 W
• B. 0.9 W
• C. 1.6 W
• D. 1.8 W

Answer 1

Answer: (C)

1.6 W

Answer 2

R_total = R for q = 180⁰

Two sections of resistance R/2 each are in parallel R_eq = R/4

\ Rate of heat flow I₁ = 1.2 = DT/R/4

Ž 0.3 = $\frac{\Delta T}{R}$

q = 90⁰ two sections of resistance R/4 & 3R/4 in parallel R_eq

= $\frac{R/4.3R/4}{R/4 + 3R/4}$ = $\frac{3R}{16}$

\ I₂ = $\frac{\Delta T}{3R/16}$ = $\frac{16}{3}$ (0.3) = 1.6 watt