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3 years ago

The diagram shows a heat engine. In which area of the diagram is unusable thermal energy detected?

Physics

2 answers:

Marat540 [252]3 years ago

7 0

Nope, I disagree with the former answer. The answer is definitely Z. <u>W area</u> (boxed with red outline) is represented as the hot reservoir while <u>Z area</u> is the cold reservoir (boxed with blue outline). X area is the heat engine itself and Y area is the work produced from thermal energy from hot reservoir. Typically, all heat engines lose some heat to the environment (based from the second law of thermodynamics) that is symbolically illustrated by the lost energy in the cold reservoir. This lost thermal energy is basically the unusable thermal energy. The higher thermal energy lost, the less efficient your heat engine is.

Minchanka [31]3 years ago

4 0

The answer is Z is unusable

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g The steam above a freshly made cup of instant coffee is really water vapor droplets condensing after evaporating from the hot

geniusboy [140]

Answer:

the final temperature = 74.33°C

Explanation:

Using the expression Q = mcΔT for the heat transfer and the change in temperature .

Here ;

Q = heat transfer

m = mass of substance

c = specific heat

ΔT = the change in temperature

The heat Q required to change the phase of a sample mass m is:

Q = m $L_v$

where;

$L_v$ is the latent heat of vaporization.

From the question ;

Let M represent the mass of the coffee that remains after evaporation is:

ΔT = $\frac{mL_v}{MC}$

where;

m = 2.50 g

M = (240 - 2.50) g = 237.5 g

$L_v$ = 539 kcal/kg

c = 1.00kcal/kg. °C

ΔT = $\frac{2.50*539 \ kcal /kg}{237.5 g *1.00 \ kcal/kg . ^0C}$

ΔT = 5.67°C

The final temperature of the coffee is:

$T_f = T_i -$ ΔT

where ;

$T_I$ = initial temperature = 80 °C

$T_f$ = (80 - 5.67)°C

$T_f$ = 74.33°C

Thus; the final temperature = 74.33°C

8 0

3 years ago

Read 2 more answers

14)

Mama L [17]

Watt is a unit for power that is also equal to J/s. We therefore need to convert the minutes to seconds first before answering. Every minute is comprised of 60 seconds. Therefore, 3 minutes are composed of 180 seconds. Multiplying the number of seconds to the given power will give us,
Work = Power x time
= (1500 J/s) x (180 s)
= 270,000 J
Therefore, the answer is letter D.

6 0

3 years ago

Which type of device enables its users to see around corners?

Dmitriy789 [7]

Answer:

We can use optical fibers.

Explanation:

The optical fibers are the optical devices which is based on the total internal reflection.

The optical fiber has two layers, one is called core and the other is called cladding.

The refractive index of core is more than the cladding.

As a ray of light falls on the core at more than the critical angle for that pair of media(core and cladding), it suffers the total internal reflection at the interface.