Home
Class 12
PHYSICS
A ring consisting of two parts ADB and A...

A ring consisting of two parts `ADB` and `ACB` of same conductivity k carries an amount of heat `H` The `ADB` part is now replaced with another metal keeping the temperature `T_91)` and `T_(2)` constant The heat carried increases to `2H` What should be the conductivity of the new `ADB` Given `(ACB)/(ADB)=3`
.

A

`(7)/(3)k`

B

`2`k

C

`(5)/(2)`k

D

`3`k

Text Solution

Verified by Experts

The correct Answer is:
A
`H=(T_(1)-T_(2))/(R)` and `2H = (T_(1)-T_(2))/(R) implies R' = (R)/(2)`
(where `R` &`R'` are thermal resistance).
`R = (1)/((L)/(kA) + (3L)/(kA)) implies R' = (1)/((kA)/(3L) + (k'A)/(3L)).`
`implies k' = (7k)/(3)` (k' = cond. Of `ADB` wire).
Promotional Banner

Topper's Solved these Questions

  • GEOMETRICAL OPTICS

    ALLEN |Exercise EXERCISE -03|11 Videos

  • GEOMETRICAL OPTICS

    ALLEN |Exercise ASSERTION-REASON|40 Videos

  • GEOMETRICAL OPTICS

    ALLEN |Exercise EXERCISE -01|65 Videos

  • CURRENT ELECTRICITY

    ALLEN |Exercise EX.II|66 Videos

  • GRAVITATION

    ALLEN |Exercise EXERCISE 4|9 Videos

Similar Questions

Explore conceptually related problems

The 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. Temperatures on the opposite faces of composite slab are T_(1) and T_(2) where T_(2)gtT_(1) , as shown in fig. what is the rate of flow of heat through the slab in a steady state?

A cylindrical block of length 0.4 m and area of cross-section 0.04 m^2 is placed coaxially on a thin metal disc of mass 0.4 kg and of the same cross - section. The upper face of the cylinder is maintained at a constant temperature of 400 K and the initial temperature of the disc is 300K . if the thermal conductivity of the material of the cylinder is 10 "watt"// m.K and the specific heat of the material of the disc is 600J//kg.K , how long will it take for the temperature of the disc to increase to 350 K ? Assume for purpose of calculation the thermal conductivity of the disc to be very high and the system to be thermally insulated except for the upper face of the cylinder.

The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity K and 2K and thicknesses x and 4x, respectively are T_(2) and T_(1)(T_(2)gtT_(1)) . The rate of heat of heat transfer through the slab, in ? steady state is [(A(T_(2)-T_(1))/(x)]f , with f equal to :-

One end of rod of length L and cross-sectional area A is kept in a furance of temperature T_(1) . The other end of the rod is kept at at temperature T_(2) . The thermal conductivity of the material of the rod is K and emissivity of the rod is e . It is given that T_(2)=T_(S)+DeltaT where DeltaT lt lt T_(S) , T_(S) being the temperature of the surroundings. If DeltaT prop (T_(1)-T_(S)) , find the proportionality constant. Consider that heat is lost only by radiation at the end where the temperature of the rod is T_(2) .

Explain why (a) Two bodies at different temperatures T_(1) and T_(2) if brought in thermal contact do not necessarily settle to the mean temperature (T_(1) + T_(2))//2 . (b) The coolant in a chemical or a nuclear plant (i.e., the liquid used to prevent the different parts of a plant from getting too hot) should have high specific heat. (c) Air pressure in a car tyre increases during driving. (d) The climate of a harbour town is more temperate than that of a town in a desert at the same latitude.

The method of electrical images is used to solve the electrostatic problems, where charge distribution is not specified completely. The method consists of replacement of given charge distribution by a simplified charge distribution or a signal point charge or a number of point charges [rovided the original boundary conditions are still satisfied. For example consider a system consider a system containing a point charge q placed at a distance d of form an infinite conducting plane. The boundary conditions are : (i) Potential is zero at infinity (ii) Potential is zero at each point on the conducting plane If we replaced the conducting plane by a point charge (-q) placed at a distance 'd' opposite to conducting plane. The charge (-q) is called the electrical image. Now system consists of two charge +q an -q at seperation 2d . If charge +q moves to a distance 'y' from the boundary of conducting plane (now absent), the electrical image -q also moves to the same 'y' from the boundary of conducting plane, so that the new distance between +q and -q is 2y The work done in carrying charge q from distance d to distance y from earthed conducting plane is

The figure shows the cross-section of the outer wall of a house buit in a hill-resort to keep the house insulated from the freezing temperature of outside. The wall consists of teak wood of thickness L_(1) and brick of thickness (L_(2) = 5L_(1)) , sandwitching two layers of an unknown material with identical thermal conductivites and thickness. The thermal conductivity of teak wood is K_(1) and that of brick is (K_(2) = 5K) . Heat conducion through the wall has reached a steady state with the temperature of three surfaces being known. (T_(1) = 25^(@)C, T_(2) = 20^(@)C and T_(5) = - 20^(@)C) . Find the interface temperature T_(4) and T_(3) .

Explain why : (a) Two bodies at different temperatures T_1 and T_2 if brought in thermal contact do not necessarily settle to the mean temperature (T_1 + T_2 )//2 . (b) The coolant in a chemical or a nuclear plant (i.e., the liquid used to prevent the different parts of a plant from getting too hot) should have high specific heat. (c) Air pressure in a car tyre increases during driving. (d)The climate of a harbour town is more temperate than that of a town in a desert at the same latitude.

An insulated cylinder is divided into three parts A, B and C. Pistons 1 and 2 are connected by a rigid rod and can slide without friction inside the cylinder. Piston 1 is perfectly conducting while piston 2 is perfectly insulating. Equal quantity of an ideal gas is filled in three compartments and the state of gas in every part is same (P_(0) V_(0) T_(0)) . Adiabatic exponent of the gas is g = 1.5. The compartment B is slowly given heat through a heater H such that the final volume of gas in part C becomes (4V_(0))/(9) (a) Calculate the heat supplied by the heater. (b) Calculate the amount of heat flow through piston 1. (c) If heater were in compartment A, instead of B how would your answers to (a) and (b) change?

Comprehension-1 Two closed identical conducting containers are found in the laboratory of an old scientist. For the vertification of the gas some experiments are performed on the two boxes and the results are noted. Experimenet 1. When the two containers are weighed W_(A) = 225tg, W_(B) = 160 g and mass of evacuated container W_(C) = 100g . Experiment 2. When the two containers are given same amount of heat same temperature rise is recorded. The pressure changes found are DeltaP_(A) = 2.5 atm, Deltap_(B) = 1.5 atm . Required data for unknown gas: |(underset("molar mass")(Mono)",He,Ne,Ar,Kr,Xe,Rd),(,4g,20g,40g,84g,131g,222g),(underset(molar mass)(Dia),H_(2),F_(2),N_(2),O_(2),CI_(2),),(,2g,19g,28g,32g,71g,)| The initial internal energy of the gas in container 'A'. If the container were at room temperature initially

ALLEN -GEOMETRICAL OPTICS-EXERCISE -02
  1. A body with an initial temperature theta(1) is allowed to cool in a su...

    Text Solution

    |

  2. A rod of length L with sides fully insulated is made of a material who...

    Text Solution

    |

  3. A ring consisting of two parts ADB and ACB of same conductivity k carr...

    Text Solution

    |

  4. Twelve conducting rods from the sides of a uniform cube of side l. If ...

    Text Solution

    |

  5. Radius of a conductor increases uniformly from left end to right end a...

    Text Solution

    |

  6. A sphere of ice at 0^(@)C having initial radius R is placed in an envi...

    Text Solution

    |

  7. Three identical rods AB, CD and PQ are joined as shown. P and Q are mi...

    Text Solution

    |

  8. Three bodies A , B and C have equal surface area and thermal emissivit...

    Text Solution

    |

  9. A and B are two points on uniform metal ring whose centre is O The ang...

    Text Solution

    |

  10. In a 10 m deep lake, the bottom is at a constant temperature of 4^(@)C...

    Text Solution

    |

  11. The solar constant for the earth is s. The surface temperature of the ...

    Text Solution

    |

  12. A system S receives heat continuously from an electric heater of power...

    Text Solution

    |

  13. If the absorption coefficient and reflection coefficient of a surface ...

    Text Solution

    |

  14. Temperature of black body is 3000K. When black body cools, then change...

    Text Solution

    |

  15. Two plates of equal areas are placed in contact with each other . Thei...

    Text Solution

    |

  16. Two identical square rods of metal are welded end to end as shown in f...

    Text Solution

    |

  17. Three rods of same dimensions are arranged as shown in Fig. They have ...

    Text Solution

    |

  18. The temperature of the two outer surfaces of a composite slab, consist...

    Text Solution

    |

  19. The figure shows a system of two concentric spheres of radii r1 and r2...

    Text Solution

    |

  20. The pressure of an ideal gas varies according to the law P = P(0) - AV...

    Text Solution

    |