| 31. | A cylindrical cement tube of radii 0.05 cm and 1.0 cm has a wire embedded into it along its axis. To maintain a steady temperature difference of 120 degree Celsius between the inner and outer surfaces, a current of 5 ampere is made to flow in the wire. Find the amount of heat generated per meter length. Take resistance of wire equal to 0.1 ohm per cm of length |
| a. | 150 W/m length |
| b. | 250 W/m length |
| c. | 350 W/m length |
| d. | 450 W/m length |
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Answer: (b).250 W/m length
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| 32. | A stainless steel tube with inner diameter₁2 mm, thickness 0.2 mm and length 50n cm is heated electrically. The entire 15 k W of heat energy generated in the tube is transferred through its outer surface. Find the intensity of current flow |
| a. | 52 amps |
| b. | 62 amps |
| c. | 72 amps |
| d. | 82 amps |
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Answer: (a).52 amps
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| 33. | The temperature distribution associated with radial conduction through a sphere is represented by |
| a. | Parabola |
| b. | Hyperbola |
| c. | Linear |
| d. | Ellipse |
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Answer: (b).Hyperbola
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| 34. | The thermal resistance for heat conduction through a spherical wall is |
| a. | (r₂-r₁)/2πkr₁r₂ |
| b. | (r₂-r₁)/3πkr₁r₂ |
| c. | (r₂-r₁)/πkr₁r₂ |
| d. | (r₂-r₁)/4πkr₁r₂ |
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Answer: (d).(r₂-r₁)/4πkr₁r₂
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| 35. | The rate of conduction heat flow in case of a composite sphere is given by |
| a. | Q = t₁ – t₂/ (r₂ – r₁)/4πk₁r₁r₂ + (r3 – r2 )/4πk₂r₂r₃ |
| b. | Q = t₁ – t₂/ (r₂ – r₁)/4πk₁r₁r₂ + (r3 – r2 )/4πk₂r₂r₃ |
| c. | Q = t₁ – t₂/ (r₂ – r₁)/4πk₁r₁r₂ + (r3 – r2 )/4πk₂r₂r₃ |
| d. | Q = t₁ – t₂/ (r₂ – r₁)/4πk₁r₁r₂ + (r3 – r2 )/4πk₂r₂r₃ |
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Answer: Q = t₁ – t₂/ (r₂ – r₁)/4πk₁r₁r₂ + (r₃ – r₂ )/4πk₂r₂r₃
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