Access and Discuss Multiple choice questions for various competitive Exams and Interviews.

1. In case of heat conduction through plane wall, which one of the following is not a correct assumption?
a. Steady state
b. Three dimensional heat flow
c. Volumetric heat generation must be constant
d. K must be constant
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Answer: (b).Three dimensional heat flow

2. If Q X is heat generated in at distance ‘x’, then heat conducted out at a distance (x + d x) will be
a. Q X + 3d (Q X) d x /d x
b. 2Q X + d (Q X) d x /d x
c. d (Q X) d x /d x
d. Q X + d (Q X) d x /d x
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Answer: (d).Q X + d (Q X) d x /d x

3. Notable example of uniform generation of heat within the conducting medium are

(i) Energy of a nuclear reactor

(ii) Liberation of energy due to some exothermic chemical reactions

(iii) Resistance heating in electrical appliances

Which of the statements made above are correct?
a. 1, 2 and 3
b. 1 and 2
c. 1 and 3
d. Only 2
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Answer: (a).1, 2 and 3

4. For a plane wall of thickness l with uniformly distributed heat generation q g per unit volume, the temperature t₀ at mid plane is given by
a. t₀ = q g l²/2k +t w
b. t₀ = q g l²/4k +t w
c. t₀ = q g l²/8k +t w
d. t₀ = q g l²/16k +t w
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Answer: (c).t₀ = q g l²/8k +t w

5. The temperature drop in a plane wall with uniformly distributed heat generation can be decreased by reducing
a. Wall thickness
b. Heat generation rate
c. Thermal conductivity
d. Surface area
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Answer: (a).Wall thickness

6. Consider a slab of thickness δ with one side (x = 0) insulated and other side (x = δ) maintained at constant temperature. The rate of uniform heat generation within the slab is q g W/m³. Presuming that the heat conduction is in steady state and one dimensional along x direction, the maximum temperature in the slab would occur at x equal
a. δ/2
b. Zero
c. δ/4
d. δ
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Answer: (b).Zero

7. There occurs heat conduction and internal heat generation at uniform rate within the conduction medium itself in the following cases
(i) Drying of concrete

(ii) Chemical processes

(iii) Fuel elements in a nuclear reaction

Choose the correct option
a. 1 only
b. 2 only
c. 1 and 3
d. 1, 2 and 3
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Answer: (d).1, 2 and 3

8. Suppose heat is conducted due to electrons
Where, i = I/A and p is the resistivity, then
a. q g = 2i² p
b. q g = 3i² p
c. q g = i² p
d. q g = 4i² p
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Answer: (c).q g = i² p

9. In case when both the surfaces of plane wall are at different temperature, we get an expression i.e.

T MAX – T W2 /T W1 – TW2 = (B + 1)²/4B

What is the value of B?
a. (q g) (δ)²/2k (T W1 – TW2)
b. (q g) (δ)³/3k (T W1 – TW2)
c. (q g) (δ)⁴/4k (T W1 – TW2)
d. (q g) (δ)⁵/5k (T W1 – TW2)
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Answer: (a).(q g) (δ)²/2k (T W1 – TW2)

10. Which one of the following materials are quickly heated by applying high frequency?
a. Textiles
b. Engines
c. Rubber
d. Coal
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Answer: (a).Textiles

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