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Three rods made of the same material and having the same cross-section have been joined as shown in the figure. Each rod has the same length. The left and right ends are kept at \(0^{\circ}\text{C}~\text{and}~90^{\circ}\text{C},\) respectively. The temperature at the junction of the three rods will be:

1. \(45^{\circ}\text{C}\)

2. \(60^{\circ}\text{C}\)

3. \(30^{\circ}\text{C}\)

4. \(20^{\circ}\text{C}\)

Subtopic: Conduction |

84%

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Hot coffee in a mug cools from \(90^{\circ}\mathrm{C}\) to \(70^{\circ}\mathrm{C}\) in 4.8 minutes. The room temperature is \(20^{\circ}\mathrm{C}\). Applying Newton's law of cooling, the time needed to cool it further by \(10^{\circ}\mathrm{C}\) should be nearly:

1. | 4.2 minute | 2. | 3.8 minute |

3. | 3.2 minute | 4. | 2.4 minute |

Subtopic: Newton's Law of Cooling |

70%

From NCERT

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One kilogram of ice at \(0^\circ \mathrm{C}\) is mixed with one kilogram of water at \(80^\circ \mathrm{C}.\) The final temperature of the mixture will be: (Take: Specific heat of water = \(4200\) J kg^{-1 }K^{-1}, latent heat of ice\(=336\) kJ kg^{-1})

1. | \(0^\circ \mathrm{C}\) | 2. | \(50^\circ \mathrm{C}\) |

3. | \(40^\circ \mathrm{C}\) | 4. | \(60^\circ \mathrm{C}\) |

Subtopic: Calorimetry |

74%

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The value of the coefficient of volume expansion of glycerin is \(5\times10^{-4}\) K^{-1}. The fractional change in the density of glycerin for a temperature increase of \(40^\circ \mathrm{C}\) will be:

1. | \(0.015\) | 2. | \(0.020\) |

3. | \(0.025\) | 4. | \(0.010\) |

Subtopic: Thermal Expansion |

82%

From NCERT

NEET - 2015

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Steam at \(100^{\circ}\mathrm{C}\) is injected into 20 g of \(10^{\circ}\mathrm{C}\) water. When water acquires a temperature of \(80^{\circ}\mathrm{C}\), the mass of water present will be: (Take specific heat of water =1 cal g^{-1} \(^\circ\)C^{-1} and latent heat of steam = 540 cal g^{-1})

1. | 24 g | 2. | 31.5g |

3. | 42.5 g | 4. | 22.5 g |

Subtopic: Calorimetry |

71%

From NCERT

NEET - 2014

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The temperature of a body falls from \(50^{\circ}\mathrm{C}\)$\mathrm{}$ to \(40^{\circ}\mathrm{C}\)$\mathrm{}$ in 10 minutes. If the temperature of the surroundings is \(20^{\circ}\mathrm{C}\)$\mathrm{,\; t}$hen the temperature of the body after another 10 minutes will be:

1. \(36.6^{\circ}\mathrm{C}\)

2. \(33.3^{\circ}\mathrm{C}\)$\mathrm{}$

3. \(35^{\circ}\mathrm{C}\)

4. \(30^{\circ}\mathrm{C}\)$\mathrm{}$

Subtopic: Newton's Law of Cooling |

79%

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Two rods (one semi-circular and the other straight) of the same material and of the same cross-sectional area are joined as shown in the figure. Points \(A\) and \(B\) are maintained at different temperatures. The ratio of the heat transferred through a cross-section of a semi-circular rod to the heat transferred through a
cross-section of a straight rod at any given point in time will be:

1. \(2:\pi\)

2. \(1:2\)

3. \(\pi:2\)

4. \(3:2\)

Subtopic: Conduction |

66%

From NCERT

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The plots of intensity versus wavelength for three black bodies at temperatures ${\mathrm{T}}_{1}$, ${\mathrm{T}}_{2}$ and ${\mathrm{T}}_{3}$ respectively are as shown. Their temperatures are such that:

1. | \(\mathrm{T}_1>\mathrm{T}_2>\mathrm{T}_3 \) | 2. | \(\mathrm{T}_1>\mathrm{T}_3>\mathrm{T}_2 \) |

3. | \(\mathrm{T}_2>\mathrm{T}_3>\mathrm{T}_1 \) | 4. | \(\mathrm{T}_3>\mathrm{T}_2>\mathrm{T}_1\) |

Subtopic: Wien's Displacement Law |

64%

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Two rods, one made of aluminium and the other made of steel, having initial lengths \(l_1\) and \(l_2\) are connected together to form a single rod of length ${l}_{1}+{l}_{2}$. The coefficient of linear expansion for aluminium and steel are ${\alpha}_{a}$ and ${\alpha}_{s}$ respectively. If the length of each rod increases by the same amount when their temperature is raised by \(t^\circ \mathrm{C},\) then the ratio \(\frac{l_1}{l_1+l_2}\) is:

1. $\frac{{\alpha}_{s}}{{\alpha}_{a}}$

2. $\frac{{\alpha}_{a}}{{\alpha}_{s}}$

3. $\frac{{\alpha}_{a}}{{\alpha}_{a}+{\alpha}_{s}}$

4. $\frac{{\alpha}_{s}}{{\alpha}_{a}+{\alpha}_{s}}$

Subtopic: Thermal Expansion |

59%

From NCERT

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Four rods of the same material with different radii \(r\)* *and length \(l\) are used to connect two heat reservoirs at different temperatures. In which of the following cases is the heat conduction fastest?

1. \(r = \frac{1}{3}~\text{cm}, l = \frac{1}{9}~\text{cm}\)

2. \(r =3~\text{cm}, l =9~\text{cm}\)

3. \(r =4~\text{cm}, l =8~\text{cm}\)

4. \(r =1~\text{cm}, l =1~\text{cm}\)

Subtopic: Conduction |

73%

From NCERT

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