A cup of tea cools from $80\,^oC$ to $60\,^oC$ in one minute. The ambient temperature is $30\,^oC$. In cooling from $60\,^oC$ to $50\,^oC$, it will take ....... $\sec$
Medium
Download our app for free and get started
$\frac{20}{60}=\mathrm{K}(70-30)$
$\frac{10}{t}=K(55-30)$
$\frac{20}{60 \times 10} \mathrm{t}=\frac{40}{25}$
$\mathrm{t}=\frac{8 \times 6 \times 10}{10}=48 \mathrm{sec}$
Download our appand get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Similar Questions
- 1Two identical plates of different metals are joined to form a single plate whose thickness is double the thickness of each plate. If the coefficients of conductivity of each plate are $2$ and $3$ respectively, then the conductivity of composite plate will beView Solution
- 2Two rods of same length and material transfer a given amount of heat in $12$ seconds, when they are joined end to end. But when they are joined lengthwise, then they will transfer same heat in same conditions in ....... $\sec$View Solution
- 3The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity $K$ and $2K$ and thickness $x$ and $4x$ , respectively are $T_2$ and $T_1$ ($T_2$ > $T_1$). The rate of heat transfer through the slab, in a steady state is $\left( {\frac{{A({T_2} - {T_1})K}}{x}} \right)f$, with $f $ which equal toView Solution
- 4Two rods of same material have same length and area. The heat $\Delta Q$ flows through them for $12\,minutes$ when they are jointed in series. If now both the rods are joined in parallel, then the same amount of heat $\Delta Q$ will flow in ........ $\min$View Solution
- 5rod of $40\, cm$ in length and temperature difference of ${80^o}C$ at its two ends. $A$ nother rod $B$ of length $60\, cm$ and of temperature difference ${90^o}C$, having the same area of cross-section. If the rate of flow of heat is the same, then the ratio of their thermal conductivities will beView Solution
- 6Find effective thermal resistance between $A$ & $B$ of cube made up of $12$ rods of same dimensions and shown given thermal conductivity. [ $l =$ length of rod, $a =$ cross section area of rod]View Solution
- 7The two ends of a rod of length $L$ and a uniform cross-sectional area $A$ are kept at two temperatures $T_1$ and $T_2 (T_1 > T_2)$. The rate of heat transfer,$\frac{ dQ }{dt}$, through the rod in a steady state is given byView Solution
- 8Distance between sun and Earth is $2 \times 10^{8}\, km ,$ temperature of sun $6000\, K ,$ radius of sun $7 \times 10^{5}\, km .$ If emmisivity of the earth is $0.6,$ find out the temperature of the earth in thermal equilibrium (in $k$)View Solution
- 9For a system with newtons law of cooling applicable the initial rate of cooling is $R^0\ C/sec$ find the time when temperature diff. $\Delta T_0 =$ initial temperature difference, is reduced to half.View Solution
- 10View SolutionWhich of the prism is used to see infra-red spectrum of light