The coefficient of thermal conductivity of copper is nine times that of steel. In the composite cylindrical bar shown in the figure. What will be the temperature at the junction of copper and steel 


(a) 75°C
(b) 67°C
(c) 33°C
(d) 25°C

Subtopic:  Conduction |
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A slab consists of two parallel layers of two different materials of same thickness having thermal conductivities K1 and K2. The equivalent conductivity of the combination is

(1) K1+K2           

(2) K1+K22

(3) 2K1K2K1+K2         

(4) K1+K22K1K2

Subtopic:  Conduction |
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There are two identical vessels filled with equal amounts of ice. The vessels are of different metals., If the ice melts in the two vessels in 20 and 35 minutes respectively, the ratio of the coefficients of thermal conductivity of the two metals is

(1) 4 : 7                   

(2) 7 : 4

(3) 16 :49                 

(4) 49 : 16

Subtopic:  Conduction |
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Heat current is maximum in which of the following (rods are of identical dimension) ?

Subtopic:  Conduction |
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Consider a compound slab consisting of two different materials having an equal thickness and thermal conductivities K and 2K respectively. The equivalent thermal conductivity of the slab if the materials are joined by ends is:
(a) 2K                  (b) 3K
(c) 43K                    (d) 23K

Subtopic:  Conduction |
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Two rods having thermal conductivity in the ratio of 5 : 3 having equal lengths and equal cross-sectional area are joined by face to face. If the temperature of the free end of the first rod is 100°C and free end of the second rod is 20°C. Then temperature of the junction is

(1) 70 °C                   

(2) 50 °C

(3) 50 °C                  

(4) 90 °C

Subtopic:  Conduction |
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Woollen clothes are used in winter season because woollen clothes

(1) Are good sources for producing heat

(2) Absorb heat from surroundings

(3) Are bad conductors of heat

(4) Provide heat to body continuously

Subtopic:  Conduction |
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Two metal cubes and of same size are arranged as shown in the figure. The extreme ends of the combination are maintained at the indicated temperatures. The arrangement is thermally insulated. The coefficients of thermal conductivity of A and B are 300 W/m°C and 200 W/m°C, respectively. After steady state is reached, the temperature of the interface will be 

(1) 45°C
(2) 90°C
(3) 30°C
(4) 60°C

Subtopic:  Conduction |
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A cylindrical rod having temperature T1 and T2 at its ends. The rate of flow of heat is Q1 cal/sec. If all the linear dimensions are doubled keeping temperature constant then rate of flow of heat Q2 will be
(a) 4Q1           (b) 2Q1
(c)Q14            (d) Q12

Subtopic:  Conduction |
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A body of length 1m having cross sectional area 0.75 m2 has heat flow through it at the rate of 6000 Joule/sec. Then find the temperature difference if K = 200 Jm-1K-1 

(a) 20°C                     (b) 40°C
(c) 80°C                     (d) 100°C

Subtopic:  Conduction |
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