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A 10 kW drilling machine is used to drill a bore in a small aluminium block of mass 8.0 kg. How much is the rise in temperature of the block in 2.5 minutes?

(Assuming 50% of power is used up in heating the machine itself or lost to the surroundings? Specific heat of aluminium $=0.91J{g}^{-1}{K}^{-1}$.)

1. 103°C

2. 109°C

3. 211°C

4. 197°C

Subtopic: Calorimetry |

56%

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In an experiment on the specific heat of a metal, a \(0.20\) kg block of the metal at \(150^{\circ}\text{C}\) is dropped in a copper calorimeter (of water equivalent of \(0.025\) kg) containing \(150~\text{cm}^{3}\) of water at \(27^{\circ}\text{C}\). The final temperature is \(40^{\circ}\text{C}\). The specific heat of the metal will be:

(Heat losses to the surroundings are negligible)

1. \(0 . 40 ~ \text{Jg}^{- 1} \text{K}^{- 1}\)

2. \(0 . 43 ~ \text{Jg}^{- 1} \text{K}^{- 1}\)

3. \(0 . 54 ~ \text{Jg}^{- 1} \text{K}^{- 1}\)

4. \(0 . 61 ~ \text{Jg}^{- 1} \text{K}^{- 1}\)

Subtopic: Calorimetry |

60%

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A copper block of mass 2.5 kg is heated in a furnace to a temperature of 500 °C and then placed on a large ice block. What is the maximum amount of ice that can melt?

(Specific heat of copper = $0.39J{g}^{-1}{K}^{-1},$ the heat of fusion of water = 335 J/g)

1. 1.32 kg

2. 1.12 kg

3. 1.45 kg

4. 1.53 kg

Subtopic: Calorimetry |

63%

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A child of mass 30 kg running at a temperature of 101°F is given an antipyrin (i.e. medicine that lowers fever) which causes an increase in the rate of evaporation of sweat from his body. If the fever is brought down to 98 °F in 20 min, what is the average rate of extra evaporation caused, by the drug?

[Assume the evaporation mechanism to be the only way by which heat is lost. The mass of the child is 30 kg. The specific heat of the human body is approximately the same as that of water, and the latent heat of evaporation of water at that temperature is about 580 cal ${g}^{-1}$.]

1. 5.81 g/min

2. 4.39 g/min

3. 8.90 g/min

4. 3.05 g/min

Subtopic: Calorimetry |

54%

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A ‘thermacole’ icebox is a cheap and efficient method for storing small quantities of

cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of

5.0 cm. If 4.0 kg of ice is put in the box, what is the amount of ice remaining after 6 h?

The outside temperature is 45 °C, and the coefficient of thermal conductivity of thermacole is $0.01J{s}^{-1}{m}^{-1}{K}^{-1}.$$\left[Heatoffusionofwater=335\times {10}^{3}Jk{g}^{-1}\right]$

1. 2.9 kg

2. 3.1 kg

3. 3.7 kg

4 4.10 kg

Subtopic: Conduction |

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A brass boiler has a base area of 0.15 ${m}^{2}$ and a thickness of 1.0 cm. It boils water at a rate of 6.0 kg/min when placed on a gas stove. What is the temperature of the part of the flame in contact with the boiler?

(Thermal conductivity of brass = $109J{s}^{-1}{m}^{-1}{K}^{-1}$, the heat of vaporization of water =$2256\times {10}^{3}J/kg$.)

1. 237.98°C

2. 150°C

3. 137.98°C

4. 100°C

Subtopic: Conduction |

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A body cools from \(80\) °C to \(50\) °C in \(5\) minutes. The time it takes to cool from \(60\) °C to \(30\) °C is:

(The temperature of the surroundings is \(20\) °C)

1. \(13\) min

2. \(15\) min

3. \(12\) min

4. \(10\) min

Subtopic: Newton's Law of Cooling |

65%

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The coefficient of volume expansion of glycerine is \(49\times 10^{-5}\) K^{–1}. What is the fractional change in its density for a \(30^\circ \text{C}\) rise in temperature?

1. \(1.44\times10^{-3}\)

2. \(1.57\times10^{-3}\)

3. \(1.57\times10^{-2}\)

4. \(1.44\times10^{-2}\)

Subtopic: Thermal Expansion |

62%

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A brass wire \(1.8\) m long at \(27\) °C is held taut with a little tension between two rigid supports. If the wire is cooled to a temperature of\(-39\) °C, what is the tension created in a wire with a diameter of \(2.0\) mm? (coefficient of linear expansion of brass \(=2.0 \times10^{-5}\) K^{–1}, Young's modulus of brass\(=0.91 \times10^{11}\) Pa)

1. \(3.8 \times 10^3\) N

2. \(3.8 \times 10^2\) N

3. \(2.9 \times 10^{-2}\) N

4. \(2.9 \times 10^{2}\) N

Subtopic: Thermal Stress |

67%

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A hole is drilled in a copper sheet. The diameter of the hole is 4.24 cm at 27.0 °C. What is the change in the diameter of the hole when the sheet is heated to 227 °C?

(Co-efficient of linear expansion of copper= $1.70\times {10}^{-5}{\mathrm{K}}^{-1}$)

1. 0.0144 cm

2. 0.0234 cm

3. 0.0123 cm

4. 0.0111 cm

Subtopic: Thermal Expansion |

60%

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