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The power radiated by a black body is $P$ and it radiates maximum energy at wavelength, $\lambda_{0}$. If the temperature of the black body is now changed so that it radiates maximum energy at wavelength $\frac{3}{4} \lambda_{0},$ the power radiated by it becomes $n P$ . The value of $n$ is

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Important Questions on Heat Transfer

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Alpha Question Bank for Medical: Physics>Chapter 16 - Heat Transfer>Exercise-3>Q 13

1 kcal

of heat flowing through a rod of iron per second. When the rod is cut down to

4

pieces then what will be the heat flowing through each piece per second having the same differential temperature (temperature gradient)?

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Alpha Question Bank for Medical: Physics>Chapter 16 - Heat Transfer>Exercise-3>Q 14

Black holes in orbit around a normal star are detected from the earth due to the frictional heating of infalling gas into the black hole, which can reach temperatures greater than

10^{6} K

. Assuming that the infalling gas can be modelled as a blackbody radiator then the wavelength of maximum power lies

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Alpha Question Bank for Medical: Physics>Chapter 16 - Heat Transfer>Exercise-3>Q 15

Two conductors having the same width and length, thickness

d_{1}

and

d_{2}

thermal conductivity

K_{1}

and

K_{2}

are placed one above the other. Find the equivalent thermal conductivity.

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Alpha Question Bank for Medical: Physics>Chapter 16 - Heat Transfer>Exercise-3>Q 16

A long metallic bar is carrying heat from one of its ends to the other end under steady-state. The variation of temperature

θ

along the length

x

of the bar from its hot end is best described by which of the following figures?

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Alpha Question Bank for Medical: Physics>Chapter 16 - Heat Transfer>Exercise-3>Q 17

If a piece of metal is heated to temperature

θ

and then allowed to cool in a room which is at temperature

θ_{0}

, the graph between the temperature

T

of the metal and time

t

will be closest to

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Alpha Question Bank for Medical: Physics>Chapter 16 - Heat Transfer>Exercise-3>Q 18

Three rods of Copper, Brass and Steel are welded together to form a Y-shaped structure. Area of cross-section of each rod is

4 {cm}^{2}

. End of copper rod is maintained at

100 ° C

. Where as ends of brass and steel are kept at

0 ° C

. Lengths of the copper, brass and steel rods are

46, 13

and

12 cms

respectively. The rods are thermally insulated from surroundings except at ends. Thermal conductivities of copper, brass and steel are

0.92, 0.26

and

0.12

CGS units respectively. Rate of heat flow through copper rod is :

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Alpha Question Bank for Medical: Physics>Chapter 16 - Heat Transfer>Exercise-3>Q 19

The temperature difference of $120 ° C$ is maintained between two ends of a uniform rod $A B$ of length $2 L$ . Another bent rod $P Q$ , of the same cross-section as $A B$ and length $\frac{3 L}{2}$ , is connected across $A B$ (see figure). In steady-state, the temperature difference between $P$ and $Q$ will be close to

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Alpha Question Bank for Medical: Physics>Chapter 16 - Heat Transfer>Exercise-3>Q 20

A heat source at

T = 10^{3} K

is connected to another heat reservoir at

T = 10^{2} K

by a copper slab which is

1 m

thick. Given that the thermal conductivity of copper is

0 .1 W K^{- 1} m^{- 1}

, the energy flux through it in the steady-state is:

The power radiated by a black body is $P$ and it radiates maximum energy at wavelength, $\lambda_{0}$. If the temperature of the black body is now changed so that it radiates maximum energy at wavelength $\frac{3}{4} \lambda_{0},$ the power radiated by it becomes nP. The value of n is

Important Questions on Heat Transfer

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The power radiated by a black body is $P$ and it radiates maximum energy at wavelength, $\lambda_{0}$. If the temperature of the black body is now changed so that it radiates maximum energy at wavelength $\frac{3}{4} \lambda_{0},$ the power radiated by it becomes $n P$ . The value of $n$ is