Transmission Of Heat Question 53
Question: The coefficients of thermal conductivity of copper, mercury and glass are respectively Kc, Km and Kg such that Kc > Km > Kg. If the same quantity of heat is to flow per second per unit area of each and corresponding temperature gradients are Xc, Xm and Xg, then
[MP PMT 1990]
Options:
A) $ X _{c}=X _{m}=X _{g} $
B) $ X _{c}>X _{m}>X _{g} $
C) $ X _{c}<X _{m}<X _{g} $
D) $ X _{m}<X _{c}<X _{g} $
Show Answer
Answer:
Correct Answer: C
Solution:
$ \frac{Q}{At}=K\frac{\Delta \theta }{l} $
Therefore $ K\frac{\Delta \theta }{l} $ = constant
Therefore $ \frac{\Delta \theta }{l}\propto \frac{1}{K} $ Hence If $ K _{c}>K _{m}>K _{g} $ , then $ {{( \frac{\Delta \theta }{l} )} _{c}}<{{( \frac{\Delta \theta }{l} )} _{m}}<{{( \frac{\Delta \theta }{l} )} _{g}}\Rightarrow X _{c}<X _{m}<X _{g} $ because higher K implies lower value of the temperature gradient.
BETA
