# Question about electrical power compared to mechanical power

• leifh
In summary, the conversation explores the use of analogies in understanding electrical and mechanical formulas. While there are some parallels between the two, it is important to use analogies sparingly and not rely on them too heavily as they can lead to confusion. The focus should be on understanding the fundamental principles and utilizing dimensional analysis to make connections between different systems.
leifh
I am new here and I am seeking for help:) Thank you so much.
In engineering, electrical formula often analogy to mechanical formula.
eg. power[W] = pressure x volume flow rate vs power[W] = voltage x current
My question is could we make the simplest unit between electrical and mechanical?

Reference: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/watcir.html#c1

1. mechanical pressure [N/m2] = voltage pressure [V]
1a. P=F/A=FR[resistance] ; V=IR
1b. Power[W]= force x velocity = force x distance/time; Could make analogy to electrical?
1c. Energy[J] = pressure x volume = pressure x area x distance;

2. volume flow rate[m3/s] = current[A]/[C/s]
2a. volume flow rate = area[m2] x velocity[m/s] current to ?
For 1a. where force = current = volume flow rate?

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What would you do with thermal, chemical and nuclear energy?

Analogies, if they are taken too far, lead to trouble. Use analogies sparingly, not desperately.

sophiecentaur, leifh, DaveE and 1 other person
Welcome to PF.

The parallels in the equations for fluids and electricity, are present at the beginning, but they fail when you get deeper into the subject, and so will lead you astray. For that reason, once you have discovered them, they are best avoided.

You might take a look at dimensional analysis, to see how that explains the parallels and analogies you see.
https://en.wikipedia.org/wiki/Dimensional_analysis

sophiecentaur, leifh and DaveE
The fact that the unit for power is the Watt for both isn't a coincidence. The unit system was designed that way. If that's what you are asking...

leifh and sophiecentaur
leifh said:
My question is could we make the simplest unit between electrical and mechanical?
There are dozens of linear equations that describe different systems but it's only the form of Maths that they have in common.

You clearly know about the Watt so why isn't that enough? That Hyperphysics page shows an analogy. The mechanical / hydraulic model should be viewed with care as an electrical analogy. Voltage is not Pressure or Force. Personally, I would question whether they should have included it in what, in most other respects, is an excellent source of Physics help.

leifh
Thank you all so much! Really appreciated. I was thinking some analogy between electrical and mechanical equation so trying to make the simplest and deepest unit or element for them by analogy mindset. It seems not correct to deepest.

sophiecentaur
leifh said:
I was thinking some analogy between electrical and mechanical equation
I have to come clean about this and I think I must be just like a lot of Engineers / Physicists. For my personal use, I have many quirky analogies - some of them involving bodily movements - but I wouldn't dream of inflicting them on anyone else - certainly not a student. Most analogies really don't translate well from brain to brain.

nsaspook and Averagesupernova
The key to any anology is to know when it is no longer useful. If a person is approaching unfamiliar territory and is beginning to become confused, that might be the clue to question whether their old trusty way of understanding something by way of anology is any longer useful. A very sharp engineer once told me that the first thing to do when something isn't making sense is to ask yourself: "What am I doing wrong?" That could include the way it's thought about.

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nsaspook and russ_watters
Averagesupernova said:
The key to any anology is to know when it is no longer useful. If a person is approaching unfamiliar territory and is beginning to become confused, that might be the clue to question whether their old trusty way of understanding something by way of anology is any longer useful. A very sharp engineer once told me that the first thing to do when something isn't making sense is to ask yourself: "What am I doing wrong?" That could include the way it's thought about.

My standard analogy usage warning.
1st year electrical apprentice: "Now tell me again, how does that voltage and current stuff work?"

Electrical instructor: "It's simple. Just think of it like water."

Meanwhile, over at the plumbers apprentice school:

1st year plumbing apprentice: "Now tell me again, how does that pressure and flow stuff work?"

Plumbing instructor: "It's simple. Just think of it like electricity."

leifh and anorlunda

## 1. What is the difference between electrical power and mechanical power?

Electrical power is the rate at which electrical energy is converted into other forms of energy, while mechanical power is the rate at which mechanical work is done. Electrical power involves the movement of electrons, while mechanical power involves the movement of objects.

## 2. Which type of power is more efficient?

It depends on the specific application. Electrical power is generally more efficient for long-distance transmission and can be easily converted into other forms of energy. Mechanical power is more efficient for tasks that require physical movement, such as transportation or machinery.

## 3. Can electrical power be converted into mechanical power?

Yes, electrical power can be converted into mechanical power through the use of electric motors. The electrical energy is converted into rotational energy, which can then be used to power machinery or other mechanical devices.

## 4. How do we measure electrical power and mechanical power?

Electrical power is measured in watts (W), while mechanical power is measured in watts or horsepower (hp). Both types of power can also be measured in kilowatts (kW) or megawatts (MW) for larger applications.

## 5. Which type of power is more commonly used in everyday life?

Electrical power is more commonly used in everyday life, as it is used to power most electronic devices and appliances. However, mechanical power is also used in various applications such as transportation, construction, and manufacturing.

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