# Properties of Solids & Liquids-Heat Transfer (NEET (NTA)-National Eligibility cum Entrance Test (Medical) Physics): Questions 29 - 32 of 40

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## Question number: 29

» Properties of Solids & Liquids » Heat Transfer » Conduction

MCQ▾

### Question

A 5 cm thick ice block is there on the surface of water in a lake. The temperature of air is - 10° C; how much time it will take to double the thickness of the block (L = 80 cal/g, K ice = 0.004 erg/s-k, d ice = 0.92 g cm -3)

### Choices

Choice (4) Response

a.

191 hours

b.

1 hour

c.

1.91 hours

d.

19.1 hours

## Question number: 30

» Properties of Solids & Liquids » Heat Transfer » Conduction

MCQ▾

### Question

Consider two hot bodies B 1 and B 2 which have temperature 100° C and 60° C respectively at t = 0. The temperature of surroundings is 50° C. The ratio of the respective rates of cooling R 1 and R 2 of these two bodies at t = 0 will be

### Choices

Choice (4) Response

a.

R 1: R 2 = 4: 5

b.

R 1: R 2 = 3: 2

c.

R 1: R 2 = 2: 3

d.

R 1: R 2 = 5: 1

## Question number: 31

» Properties of Solids & Liquids » Heat Transfer » Convection

MCQ▾

### Question

A composite metal bar of uniform section is made up of length 25 cm of copper, 10 cm of nickel and 15 cm of aluminum. Each part being in perfect thermal contact with the adjoining part. The copper end of the composite rod is maintained at 100°C and the aluminum end at 0°C. The whole rod is covered with belt so that there is no heat loss occurs at the sides. If K Cu = 2Kal and Ka1 = 3K Ni, then what will be the temperatures of Cu - Ni and Ni - Al junctions respectively

### Choices

Choice (4) Response

a.

30°C and 50°C

b.

23.33°C and 78.8°C

c.

50°C and 30°C

d.

83.33°C and 20°C

## Question number: 32

» Properties of Solids & Liquids » Heat Transfer » Conduction

MCQ▾

### Question

An ice box used for keeping eatable cold has a total wall, area of 1 metre 2 and a wall thickness of 5.0 cm. The thermal conductivity of the ice box is K = 0.01 joule/meter °C. is filled with ice at 0° C along with eatables on a day when the temperature is 40°C. The latent heat of fusion of ice is 334 × 10 3 joules/kg. The amount of ice melted in one day is (1 day = 86400 seconds)

### Choices

Choice (4) Response

a.

7760 gm

b.

1552 gm

c.

2776 gm

d.

2069 gm

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