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Two conducting rods $A$ and $B$ of same length and cross-sectional area are connected $(i)$ In series $(ii)$ In parallel as shown. In both combination a temperature difference of $100^o C$ is maintained. If thermal conductivity of $A$ is $3K$ and that of $B$ is $K$ then the ratio of heat current flowing in parallel combination to that flowing in series combination is
A black body at a temperature of $127°C$ radiates heat at the rate of $1 cal/cm^2 × sec$. At a temperature of $527°C$ the rate of heat radiation from the body in ($cal/cm^2 × sec$) will be
A black body radiates $ 20\,W$ at temperature ${227^o}C$. If temperature of the black body is changed to ${727^o}C$ then its radiating power will be ..... $W$
A cylindrical steel rod of length $0.10 \,m$ and thermal conductivity $50 \,Wm ^{-1} K ^{-1}$ is welded end to end to copper rod of thermal conductivity $400 \,Wm ^{-1} K ^{-1}$ and of the same area of cross-section but $0.20 \,m$ long. The free end of the steel rod is maintained at $100^{\circ} C$ and that of the copper rod at $0^{\circ} C$. Assuming that the rods are perfectly insulated from the surrounding, the temperature at the junction of the two rods is ................... $^{\circ} C$
The coefficient of linear expansion of brass and steel are ${\alpha _1}$ and ${\alpha _2}$. If we take a brass rod of length ${l_1}$ and steel rod of length ${l_2}$ at $0°C$, their difference in length $({l_2} - {l_1})$ will remain the same at a temperature if
If the radius of a star is $R$ and it acts as a black body, what would be the temperature of the star, in which the rate of energy production is Q? ( $\sigma$ stands for Stefan's constant.)
The area of a hole of heat furnace is ${10^{ - 4}}{m^2}$. It radiates $1.58 \times {10^5}$ calories of heat per hour. If the emissivity of the furnace is $0.80$ , then its temperature is....... $K$
A black body is at a temperature of $5760\ K$. The energy of radiation emitted by the body at wavelength $250\ nm$ is $U_1$, at wavelength $500\ nm$ is $U_2$ and that at $1000\ nm$ is $U_3$. Wien's constant, $b = 2.88 \times 10^6\ nm\ K$. Which of the following is correct?
In a certain planetary system, it is observed that one of the celestial bodies having a surface temperature of $200 \;K$, emits radiation of maximum intensity near the wavelength $12\; \mu m$. The surface temperature (in $K$) of a nearby star which emits light of maximum intensity at a wavelength $\lambda= 4800\;\mathring A$ is