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nikklg [1K]
3 years ago
11

A thermoelectric refrigerator is powered by a 16-V power supply that draws 2.9 A of current. If the refrigerator cools down 3.1

kg of water from 25 °C to 11 °C in 12 hours, what is the average COP of the refrigerator? Take the specific heat of water as 4180 J/kg.K. (3 decimal digits)
Engineering
1 answer:
Viktor [21]3 years ago
8 0

Answer:

COP = 0.090

Explanation:

The general formula for COP is:

COP = Desired Output/Required Input

Here,

Desired Output = Heat removed from water while cooling

Desired Output = (Specific Heat of Water)(Mass of Water)(Change in Temperature)/Time

Desired Output = [(4180 J/kg.k)(3.1 kg)(25 - 11)k]/[(12 hr)(3600 sec/hr)]

Desired Output = 4.199 W

And the required input can be given as electrical power:

Required Input = Electrical Power = (Current)(Voltage)

Required Input = (2.9 A)(16 V) = 46.4 W

Therefore:

COP = 4.199 W/46.4 W

<u>COP = 0.090</u>

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Answer:

The correct answer is option 'B': Load is far from fulcrum and the effort is applied near the fulcrum

Explanation:

A lever works on the principle of balancing of torques. The torque about the fulcrum by the load should be equal to the torque by the applied effort. Since we know that the torque is proportional to both the force and the distance it is applied from the distance from the axis of rotation. A lever is used when we need to lift a heavy load by utilizing this effect of the lever arm.

A mechanical disadvantage occurs when we are not able to lift the weight easily due to the fact we apply effort near the fulcrum.

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3 years ago
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2 years ago
A cylinder of aluminum-magnesium alloy 0.5 m long is subjected to an elastic tensile stress of 10.2 MPa. The measured elastic el
elena55 [62]

Answer:

E= 15 GPa.

Explanation:

Given that

Length ,L = 0.5 m

Tensile stress ,σ = 10.2 MPa

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lets take young modulus  = E

We know that strain ε given as

\varepsilon =\dfrac{\Delta L}{L}

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\varepsilon =0.00068

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\sigma = \varepsilon  E\\\\E=\dfrac{10.2}{0.00068}\\E= 15000\ MPa\\E=15\ GPa

Therefore the young's modulus will be 15 GPa.

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3 years ago
A single Gates Rubber V belt is to be selected to deliver engine power to the wheel-drive transmission of a riding tractor. A 5-
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Hello there, please check step by step explanations to get answers.

Explanation:

Given that:

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The precautions that should be taken to avoid the overloading of domestic electric circuits are:

  1. Do not put high voltage wires in one socket.
  2. Do not use many electric appliances of high power at the same time.
<h3>What are electric circuits?</h3>

Electric circuits are wires or devices that give electricity to devices that run on electricity. Running of electric devices should be done carefully because our body can come in contact with the current.

Thus, the precautions are to keep high voltage lines away from one socket. Use only a few high-power electric appliances at once.

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