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Two rods of identical dimensions are joined end-to-end, and the ends of the composite rod are kept at \(0^\circ\mathrm{ C}\) and \(100^\circ\mathrm{ C}\) (as shown in the diagram). The temperature of the joint is found to be \(40^\circ\mathrm{ C}.\) Assuming no loss of heat through the sides of the rods, the ratio of the conductivities of the rods \(K_1/K_2\) is:

1. \(\frac32\)

2. \(\frac23\)

3. \(\frac11\)

4. \(\frac{\sqrt3}{\sqrt2}\)

Subtopic: Conduction |

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The temperature at which the Celsius and Fahrenheit thermometers agree (to give the same numerical value) is:

1. \(-40^\circ\)

2. \(40^\circ\)

3. \(0^\circ\)

4. \(50^\circ\)

Subtopic: Temperature and Heat |

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The ice-point reading on a thermometer scale is found to be \(20^\circ,\) while the steam point is found to be \(70^\circ.\) When this thermometer reads \(100^\circ ,\) the actual temperature is:

1. \(80^\circ~\mathrm{C}\)

2. \(130^\circ~\mathrm{C}\)

3. \(160^\circ~\mathrm{C}\)

4. \(200^\circ~\mathrm{C}\)

Subtopic: Temperature and Heat |

78%

From NCERT

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A rod \(\mathrm{A}\) has a coefficient of thermal expansion \((\alpha_A)\) which is twice of that of rod \(\mathrm{B}\) \((\alpha_B)\). The two rods have length \(l_A,~l_B\) where \(l_A=2l_B\). If the two rods were joined end-to-end, the average coefficient of thermal expansion is:

1. \(\alpha_A\)

2. \(\frac{2\alpha_A}{6}\)

3. \(\frac{4\alpha_A}{6}\)

4. \(\frac{5\alpha_A}{6}\)

Subtopic: Thermal Expansion |

61%

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If the ends of the meter stick are maintained at \(\theta_1\)\(^\circ \text{C}\) and \(\theta_2\)\(^\circ \text{C},\) the temperatures measured at the \(25\) cm and \(80\) cm marks are observed to be \(35^\circ \text{C}\) and \(68^\circ \text{C}\) respectively. Then the temperatures of the left end (\(\theta_1\)\(^\circ \text{C}\)) and the right end (\(\theta_2\)\(^\circ \text{C}\)) are:

1. | \(\theta_{1}=0, ~\theta_{2}=90\) |

2. | \(\theta_{1}=10,~\theta_{2}=85\) |

3. | \(\theta_{1}=20, ~\theta_{2}=80\) |

4. | \(\theta_{1}=30, ~\theta_{2}=100\) |

Subtopic: Conduction |

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When the temperature difference between a body and its surroundings is \(20\)°C, it loses heat to the surroundings at a rate of \(40\) W. If the temperature difference increases to \(25\)°C, the rate of loss of heat is:

1. \(45\) W

2. \(50\) W

3. \(60\) W

4. \(80\) W

1. \(45\) W

2. \(50\) W

3. \(60\) W

4. \(80\) W

Subtopic: Newton's Law of Cooling |

76%

From NCERT

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Two liquids flow through a heat exchanger and exchange heat energy.

The first liquid has a mass flow rate \(\Big(\dfrac{dm}{dt}\Big)=r_1,\) and its temperature rises by \(\Delta\theta_1.\) For the second liquid, the flow rate \(\Big(\dfrac{dm}{dt}\Big)=r_2,\) and the temperature fall is \(\Delta\theta_2.\) The ratio of their specific heat capacities is:

1. \(\dfrac{\Delta\theta_1}{\Delta\theta_2}\)

2. \(\dfrac{r_1}{r_2}\)

3. \(\dfrac{r_2\Delta\theta_2}{r_1\Delta\theta_1}\)

4. \(\dfrac{r_2\Delta\theta_1}{r_1\Delta\theta_2}\)

The first liquid has a mass flow rate \(\Big(\dfrac{dm}{dt}\Big)=r_1,\) and its temperature rises by \(\Delta\theta_1.\) For the second liquid, the flow rate \(\Big(\dfrac{dm}{dt}\Big)=r_2,\) and the temperature fall is \(\Delta\theta_2.\) The ratio of their specific heat capacities is:

1. \(\dfrac{\Delta\theta_1}{\Delta\theta_2}\)

2. \(\dfrac{r_1}{r_2}\)

3. \(\dfrac{r_2\Delta\theta_2}{r_1\Delta\theta_1}\)

4. \(\dfrac{r_2\Delta\theta_1}{r_1\Delta\theta_2}\)

Subtopic: Calorimetry |

73%

From NCERT

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A body cools from \(52^\circ \text{C}\) to \(48^\circ \text{C}\) in \(6\) minutes. How much time will the same body take to cool from \(53^\circ \text{C}\) to \(47^\circ \text{C}?\) Assume cooling is linear with time.

1. \(12\) minutes

2. \(9\) minutes

3. \(8\) minutes

4. \(7\) minutes

1. \(12\) minutes

2. \(9\) minutes

3. \(8\) minutes

4. \(7\) minutes

Subtopic: Newton's Law of Cooling |

82%

From NCERT

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A solid at temperature T_{1}, is kept in an evacuated chamber at temperature T_{2} > T_{1} . The rate of increase of temperature of the body is proportional to

1. T_{2 }– T_{1}

2. \(T^2_2 -T^2_1\)n

3. \(T^3_2 -T^3_1\)

4. \(T^4_2 -T^4_1\)

Subtopic: Stefan-Boltzmann Law |

80%

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In a room containing air, heat can go from one place to another:

1. by conduction only

2. by convection only

3. by radiation only

4. by all three modes

Subtopic: Convection |

62%

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