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Marina86 [1]
3 years ago
7

What colour is best for radiative heat transfer? a. Black b. Brown c. Blue d. White

Engineering
1 answer:
GarryVolchara [31]3 years ago
8 0

Answer:

The correct answer is option 'a': Black

Explanation:

As we know that for an object which is black in color it absorbs all the electromagnetic radiation's that are incident on it. Thus if we need to transfer energy to an object by radiation the most suitable color for the process  is black.

In contrast to black color white color is an excellent reflector, reflecting all the incident radiation that may be incident on it hence is the least suitable material for radiative heat transfer.

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Consider a flat plate that is 25 mm long, 30 mm wide, and 1 mm thick and a 50 mm long cylinder with the same volume as the plate
Blizzard [7]

Answer:

Average heat transfer =42.448w/m^2k

Nud = 13.45978

Explanation:

See attachment for step by step guide

4 0
3 years ago
Relay contacts that are defined as being normally open (n.o.) have contacts that are:_____.
Reptile [31]

Relay contacts that are defined as being normally open (n.o.) have contacts that are open only if  the relay coil is known to have de-energized.

<h3>What is meant by normally open contacts?</h3>

Normally open (NO) are  known to be open if there is no measure of current that is flowing through a given coil but it often close as soon as the coil is said to be energized.

Note that  Normally closed (NO) contacts are said to be closed only if the coil is said to be de-energized and open only if the coil is said to carry current or is known to have energized.

The role of relay contact is wide. The Relays are tools that are often used in the work of  switching of control circuits and it is one that  a person cannot used for power switching that has relatively bigger ampacity.

Therefore, Relay contacts that are defined as being normally open (n.o.) have contacts that are open only if  the relay coil is known to have de-energized.

Learn more about Relay contacts from

brainly.com/question/15334861
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8 0
1 year ago
What is Maglev Technology?<br> I don't want a copied and pasted answer please.
Levart [38]

Answer:

I do not know much but I looked and read, this I learned I hope this is good

The Maglev is a system of train transportation that uses two sets of magnets

working repel one another when matching poles face each other. Here, both magnetic attraction and repulsion are used to move the train car along the guideway.

Explanation:

Brainliest please

5 0
3 years ago
Whats 47,000 resistance converted to kilo or mega ohms.
Julli [10]
  1. The conversion of 47,000 Ohms to kilo-ohms is equal to 47 kilo-ohms.
  2. The conversion of 47,000 Ohms to mega-ohms is equal to 0.047 kilo-ohms.

<h3>What is resistance?</h3>

Resistance can be defined as an opposition to the flow of current in an electric circuit. Also, the standard unit of measurement of the resistance of an electric component is Ohms, which can be converted to kilo-ohms or mega-ohms.

For Ohms to kilo-ohms, we have:

1 Ohms = 0.001 kilo-ohms

47,000 Ohms = X kilo-ohms

Cross-multiplying, we have:

X = 0.001 × 47000

X = 47 kilo-ohms.

For Ohms to mega-ohms, we have:

1,000,000 ohms = 1 mega-ohms

47,000 Ohms = X mega-ohms

Cross-multiplying, we have:

X1,000,000 = 47,000

X = 47,000/1,000,000

X = 0.047 kilo-ohms.

Read more resistance here: brainly.com/question/19582164

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7 0
1 year ago
Air is compressed by a 40-kW compressor from P1 to P2. The air temperature is maintained constant at 25°C during this process a
AlexFokin [52]

Answer:

the rate of entropy change of the air is -0.1342 kW/K

the assumptions made in solving this problem

- Air is an ideal gas.

- the process is isothermal ( internally reversible process ). the change in internal energy is 0.

- It is a steady flow process

- Potential and Kinetic energy changes are negligible.

Explanation:

Given the data in the question;

From the first law of thermodynamics;

dQ = dU + dW ------ let this be equation 1

where dQ is the heat transfer, dU is internal energy and dW is the work done.

from the question, the process is isothermal ( internally reversible process )

Thus, the change in internal energy is 0

dU = 0

given that; Air is compressed by a 40-kW compressor from P1 to P2

since it is compressed, dW = -40 kW

we substitute into equation 1

dQ = 0 + ( -40 kW )

dQ = -40 kW

Now, change in entropy of air is;

ΔS_{air = dQ / T

given that T = 25 °C = ( 25 + 273.15 ) K = 298.15 K

so we substitute

ΔS_{air =  -40 kW / 298.15 K

ΔS_{air =  -0.13416 ≈ -0.1342 kW/K

Therefore, the rate of entropy change of the air is -0.1342 kW/K

the assumptions made in solving this problem

- Air is an ideal gas.

- the process is isothermal ( internally reversible process ). the change in internal energy is 0.

- It is a steady flow process

- Potential and Kinetic energy changes are negligible.

7 0
3 years ago
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