Question

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Answer 1

1 )

Formula of co efficient :

Co efficient of performance = $\beta$ = $\frac{T_2}{T_1-T_2}$

T2 = - 10 C = - 10 + 273 = 263 K

T1 = 25 C = 25 + 273 = 298 K

Co efficient = T2/(T1 - T2 )

= 263/( 298 - 263 )

= 263 / 35

= 7.51 approx .

The co efficient is 7.51 approx.

2 )

Yes refrigerator is an efficient room heater because it liberates heat energy . It gives Q1 unit of heat energy upon consuming W power . hence it is responsible for heating the surrounding and hence it is called an efficient room heater . You will also notice that any object dissipates heat energy whenever conversion takes place . Thus this is the reason .

Answer 2

ANSWER

4.
REFER TO ATTACHMENT for diagram


1)

Here T1 and T2 should be in kelvin.

Hence,we get=>

T1 = 25 C=>(25 + 273)= 298 K

T2 =(-10 C)=>(-10 + 273) = 263 K

Now,

B = T2/(T1-T2)

=>B = 263/(298-263)

=>B = 264/35

=>B = 3.5

Hence,the coefficient of performance of a refrigerator is 3.5 when it is working between -10°c and 25°c.

2)Yes,refrigerator is an efficient room heater beacuse=>

a)It is using electrical power and thus it also dissipating heat energy.Q1 unit of heat energy upon consuming W power .

b) Thus it is heating up its surrounding environment due to dissipation of electrical energy in form of heating.

c) According to Joules law of heating=>Heat produced in a conductor is directly proportional to square of current flowing through it, resistance of the conductor and time for which the it is used.

So, H =I ^2×R ×T.

Remember=>

Formula of co efficient :

Co efficient of performance =

B = T2/(T1-T2)