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Heat and Thermodynamics question

2015 · Q147
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Heat and Thermodynamics question

2015 · Q147

NEETPhysicsHeat and ThermodynamicsMCQ+4 / −1
The coefficient of performance of a refrigerator is 5. If the temperature inside freezer is −-−20oC, the temperature of the surroundings to which it rejects heat is
  1. A
    11oC
  2. B
    21oC
  3. C
    31oC
  4. D
    41oC
View written solutionFree

Correct answer: C

Coefficient of performance,

Cop=T2T1−T2Cop = {{{T_2}} \over {{T_1} - {T_2}}}Cop=T1​−T2​T2​​

5=273−20T1−(273−20)=253T1−2535 = {{273 - 20} \over {{T_1} - \left( {273 - 20} \right)}} = {{253} \over {{T_1} - 253}}5=T1​−(273−20)273−20​=T1​−253253​

5T1 – (5 × 253) = 253

5T1 = 253 + (5 × 253) = 1518

∴\therefore∴ T1=15185=303.6{T_1} = {{1518} \over 5} = 303.6T1​=51518​=303.6

⇒\Rightarrow⇒ T1 = 303.6 – 273 = 30.6 ≅\cong≅ 31°C

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