1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
patriot [66]
3 years ago
6

A heat engine running backward is called a refrigerator if its purpose is to extract heat from a cold reservoir. The same engine

running backward is called a heat pump if its purpose is to exhaust warm air into the hot reservoir. Heat pumps are widely used for home heating. You can think of a heat pump as a refrigerator that is cooling the already cold outdoors and, with its exhaust heat QH, warming the indoors. Perhaps this seems a little silly, but consider the following. Electricity can be directly used to heat a home by passing an electric current through a heating coil. This is a direct, 100% conversion of work to heat. That is, 20.0 kW of electric power (generated by doing work at the rate 20.0 kJ/s at the power plant) produces heat energy inside the home at a rate of 20.0 kJ/s. Suppose that the neighbor's home has a heat pump with a coefficient of performance of 3.00, a realistic value. NOTE: With a refrigerator, "what you get" is heat removed. But with a heat pump, "what you get" is heat delivered. So the coefficient of performance of a heat pump is K=QH/Win. An average price for electricity is about 40 MJ per dollar. A furnace or heat pump will run typically 300 hours per month during the winter.
a. How much electric power (in kW) does the heat pump use to deliver 15 kJ/s of heat energy to the house?
b. An average price for electricity is about 40 MJ per dollar. A fumace or heat pump will run typically 200 hours per month during the winter. What does one month's heating cost in the home with a 15kW electric heater and in the home of the neighbor who uses an aquivalent heat pump?
Physics
1 answer:
Alex787 [66]3 years ago
7 0

Solution :

A refrigerator is a heat engine running backwards with its main aim is to extract heat from the cold reservoir. When the engine running backwards is used to exhaust or give out hot air into a hot reservoir is known as a heat pump.

Given :

Coefficient of performance of the heat pump, COP = 3

We know COP of heat pump is K  $=\frac{Q_h}{W_{in}}$

a). Therefore the COP can also be written as :

  $COP=\frac{T_h}{T_h-T_c}$

           $=\frac{Q_h}{W_{in}}$

          $=\frac{Q_h}{P_{in}}$

∴ $3=\frac{15}{P_{in}}$

  $P_{in }=\frac{15}{3}$

        = 5 kW

b). The heating cost in a home of one month with a 15 kW electric heater can be calculated as :

  1 dollar = 40 MJ (given)

∴ $1 / 40000 kWh (15 kW)(200 x 3600 s)

    = $ 270

You might be interested in
Why are lamps connected in parrells rather than in a series in domestic circuit
Lilit [14]

Answer:

so that each component has the same voltage.

Explanation:

5 0
3 years ago
Read 2 more answers
With speeds up to 90 miles per hour, what is the fastest sport on ice?.
Eddi Din [679]

Answer:

Luge

Explanation:

8 0
3 years ago
How much work must be done to bring three electrons from a great distance apart to 5.0×10^−10 m from one another (at the corners
Inessa05 [86]

Answer:

1.38 x 10^-18 J

Explanation:

q = - 1.6 x 10^-19 C

d = 5 x 10^-10 m

the potential energy of the system gives the value of work done

The formula for the potential energy is given by

U =\frac{Kq_{1}q_{2}}{d}

So, the total potential energy of teh system is

U =\frac{Kq_{1}q_{2}}{d}+\frac{Kq_{2}q_{3}}{d}+\frac{Kq_{1}q_{3}}{d}

As all the charges are same and the distance between the two charges is same so the total potential energy becomes

U =3\times \frac{Kq^{2}}{d}

K = 9 x 10^9 Nm^2/C^2

By substituting the values

U =3\times \frac{9\times 10^{9}\times \ 1.6 \times 1.6 \times 10^{-38}}{5\times 10^{-10}}

U = 1.38 x 10^-18 J

6 0
4 years ago
I have multiple questions!
UNO [17]

I'm not sure about the rest but for question 2:

A theory is an attempt to come up with a big picture of all we know so far. It also drives future research as people do experiments to see if what the theory predicts actually happens. When experiments don’t support the theory, you have to change the theory and try again. That’s how science works. We come up with a “best guess” (theory), and then do research to test it’s accuracy. As we discover contradictions, we adjust the theory to take those into account, and then start testing the validity of the new theory.

3 0
3 years ago
A ray in glass arrives at the glass-water interface at an angle of 48° with the normal. The refracted ray, in water, makes a 72°
dimaraw [331]

Answer:

50.4°

Explanation:

Snell's law states:

n₁ sin θ₁ = n₂ sin θ₂

where n is the index of refraction and θ is the angle of incidence (relative to the normal).

When θ₁ = 48°:

n sin 48° = 1.33 sin 72°

n = 1.702

When θ₁ = 37°:

1.702 sin 37° = 1.33 sin θ

θ = 50.4°

3 0
4 years ago
Other questions:
  • 1. This image shows the various forces acting on a block of rock situated on a rock slope. What does arrow 4 represent?
    13·2 answers
  • Which statement is true about air pressure acting in an object
    13·1 answer
  • The velocity of an object is equal to the distance divided by time. The equation is velocity = distance/time. If you wanted to c
    14·1 answer
  • When 6.0 L of He(g) and 10. L of N2(g), both at 0oC and 1.0 atm, are pumped into an evacuated 4.0 L rigid container, the final p
    14·1 answer
  • A solid object has a mass of 104 kg and a volume of 1,278 m3. What is its density?
    8·1 answer
  • When the early universe cooled enough for atoms to form, _____ began.
    10·2 answers
  • Why is the heliocentric model not correct
    6·2 answers
  • When a body is accelerated under water, some of the surrounding water is also accelerated. This makes the body appear to have a
    15·1 answer
  • So this helicopter pilot dropped me in the middle of an absolutely smooth frictionless
    10·2 answers
  • Suppose the position of a particle moving along the x-axis given by the equation X=(1m/s²)t²-(5m/s)t +0.5m
    9·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!