# The thermal conductivity in S.I. units is expressed as

1.  J/m2 K

2.  W/mK

3.  W/m K sec

4.  W/m2

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W/mK

Explanation :
No Explanation available for this question

# Two blocks with masses M and m are in contact with each other and are resting on a horizontal frictionless floor. When horizontal force is applied to the heavier, the blocks accelerate to the right. The force between the two blocks is

1.  (M+m)F/m

2.  MF/m

3.  mF/M

4.  mF/(M+m)

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mF/(M+m)

Explanation :
No Explanation available for this question

# Coefficient of thermal conductivity is defined as the heat flow per unit time

1.  Through unit thickness

2.  When temperature difference of unity is maintained between opposite faces

3.  When temperature gradient is unity

4.  Across unit area when temperature gradient is unity

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Explanation :
No Explanation available for this question

# Find efficiency deals with

1.  Thermal performance

2.  Economical material requirement

3.  Cost of manufacturing

4.  All of these

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Thermal performance

Explanation :
No Explanation available for this question

# A particle starts from rest with a constant acceleration α m/sec2 and after some time it deaccelerates at a uniform rate of β m/sec2 till it comes to rest. If the total time taken between two rests position is t, then maximum velocity acquired by the particular would be

1.  (α+β/2)t

2.  (α-β/2)t

3.  (αβ/ α+β)t

4.  (α+β/α-β)t

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(αβ/ α+β)t

Explanation :
No Explanation available for this question

# The overall heat transfer coefficient (U) for a composite wall of thickness x1, x2, x3 and of corresponding thermal conductivities k1, k2, k3 is given by equation

1.  1/U = (k1/x1) + (k2/x2) + (k3/x3)

2.  U = (k1/x1) + (k2/x2) + (k3/x3)

3.  1/U = (x1/k1) + (x2/k2) + (x3/k3)

4.  U = (x1/k1) + (x2/k2) + (x3/k3)

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1/U = (x1/k1) + (x2/k2) + (x3/k3)

Explanation :
No Explanation available for this question

# A composite wall of two layers of thickness x1, ? x2 and of thermal conductivities k1 and k2 is having cross-sectional area a normal to the path of heat flow. If the wall surface temperatures are T1 and T3, then rate of heat flow (Q) is equal to

1.  A (T1 – T3)/[(x1/k2) + (?x2/k1)]

2.  A k1k2 (T1 – T3)/ (?x1 + ?x2)

3.  (Ak1 + Ak2) (T1 – T3)/ (?x1 + ?x2)

4.  (T1 – T3)/ [(?x1/Ak1) + (?x2/?k2)]

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A (T1 – T3)/[(x1/k2) + (?x2/k1)]

Explanation :
No Explanation available for this question

# In a future the wall thickness is 60 cm and is 100 wide and 150 cm high of material with thermal conductivity 0.4 W/mK. The temperature inside and outside are 10000 and 40 C respectively. The thermal resistance is

1.  1 k/W

2.  2 k/W

3.  18 k/W

4.  15 k/W

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1 k/W

Explanation :
No Explanation available for this question

# Three metal walls of the same cross-sectional area having thermal conductivities in the ratio 1: 2: 4 transfer heat at the rate of 6000 kJ/hr. For the same wall thickness, the temperature drops will be in the ratio

1.  1: 2: 4

2.  1: 1/2: 1/4

3.  1/4: 1/2: 1

4.  1: 1: 1

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1: 1/2: 1/4

Explanation :
No Explanation available for this question

1.  60 km/hr

2.  80 km/hr

3.  100 km/hr

4.  125 km/hr

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