# Identifying the various forms of Energy

1. Apr 14, 2012

### Vernewells

Hi, I’m currently doing research for a science fiction story and was wondering if anyone would be interested in helping me out.

I’m trying to understand the various applications of different forms of energy. More specifically, here is what I want to know: If someone was equipped with a machine that could directly manipulate various forms of energy to produce work at different levels, what would be the limits of such manipulations (eg: using thermal energy can cause objects to combust, but cannot create fire out of thin air as far as I know). However, before trying to get this particular question answered, I need help identifying which forms of energy can be manipulated in order to affect the environment.

From what I understand, there are 7 to 9 primary forms of energy: Mechanical (often broken down into different parts), Thermal, Radiant, Nuclear, Sound, Magnetic, Electric, Luminous and MASS. Some of these consist of potential energy (nuclear), some kinetic (thermal), and others can manifest both states (mechanic).

Unless I’m mistaken, potential forms of energy cannot be used directly to affect the environment, they must be converted into kinetic forms of energy (eg: splitting atoms leads to the conversion of nuclear energy into a wide variety of different forms of kinetic energy). Therefore, a mechanism that would permit one to manipulate energy would not be able to directly use potential energy to affect things. If one would wish to cause an object to combust, it would require either the use of radiant or thermal energy (the power of which could be taken from potential energies or from already present kinetic energies).

If the above statement is correct, it would mean that my research will have to focus on the manipulation of kinetic states of energy.

What I wish to ask is what are the different forms of energy (did I list the right ones) and which ones can be directly used to do work? I apologize in advance if my inquiry appears superfluous and overtly basic. Despite having studied physics in college, none of my professors ever ended up discussing energy forms as such (the fact I only took two courses probably didn’t help). I’ll try to make my next topic more complex and engaging .

Once I get this answered, I’ll open up a second discussion specifically aimed at answering my initial question: What are the limitations of manipulating various forms of energy?

Vernewells

2. Apr 15, 2012

### Vernewells

I’ve been doing some additional research and here is what I’ve come up with.

Energies that can directly perform work are: mechanical (motion), thermal, radiant (the electromagnetic spectrum), electrical, and sound energies.

Energies that are solely potential would therefore include mechanical (chemical, gravitational, etc...), nuclear, and electrical energies.

I’m still unsure about magnetic energy. From what I’ve read, some place it as being within the domain of electrical energy. However, isn’t magnetic energy kinetic?

In regards to luminous energy, it is apparently viewed as separate from radiant energy; however, I fail to see how the two differ in terms of practical application.

Finally, I have no clue of what to do with MASS energy. Some have equated it to Nuclear energy, although I doubt this is correct. I assume I could always regard it as a form of potential energy (and therefore ignore it for my research). There is also the issue that the different uses of mass as energy are mainly theoretical. Yet, despite this, I would still be interested in knowing what exactly could be done with it.

Any advice would be greatly appreciated.

3. Apr 16, 2012

### haruspex

I don't see a distinction between radiant and luminous.
You missed gravitational potential energy (unless that's what you meant by mass) and chemical energy.

Each form of energy is associated with a force.

The distinctions between the forms of energy are often blurred. Sound energy is a constant back and forth between kinetic and mechanical (pressure). Radiant energy is a similar back and forth between electrical and magnetic. A wave on the beach alternates gravitational with kinetic. In each case, the oscillation is what drives the wave.

According to relativity, there's no real distinction between kinetic energy and mass energy (in the E=mc^2 sense). An object moving relative to you appears to be more massive than the identical object seen as being at rest. The difference in the mass, converted via E=mc^2, is what you call kinetic energy.

Chemical energy is electrical energy at the atomic scale.

It's not true that you always have to convert via kinetic. A battery converts chemical to electricity; a leaf converts radiant to electrical to chemical.

Heat energy is kinetic, on a fine scale.

Energy cannot always be converted between forms freely. You are constrained by the laws of thermodynamics: entropy does not decrease. This applies to all forms of energy, but is most obvious in the case of converting from heat. Mostly, you need a temperature difference available. A coal-fired power station would not work without access to water (or air) at a lower temperature than the burning coal. (There are ways to satisfy the entropy rule without requiring a lower temperature "heat sink". Some physical processes can do work, going cooler in the process, by increasing the entropy in some other way. You can make a simple refrigerator from salt and fresh water.)

The entropy law also prohibits e.g. converting infrared radiation to the same quantity of energy in the form of visible light.

Not sure what you mean by "mass" energy. Did you mean gravitational, or are you thinking E=mc^2? If the second, it's no different from what's commonly meant by nuclear energy.

"Fire" is an ionised gas, or 'plasma'. This means the atoms have been so excited that electrons have been knocked right out of them, producing a cloud of electrons and positively charged ions. These keep recombining, emitting light, and getting split again by the abundance of energy around them. Heat can indeed induce this state directly.

4. Apr 16, 2012

### Vernewells

Thanks for the reply. It has helped me further understand what energy actually is.

From what I can now tell, 'energies' are categories we've come up with to describe what is actually a single phenomena; one that we view as having different manifestations. This categorization permits us to gain a better grasp of the world, even though there is no real clear cut separation between the different forms of energy (they are constantly moving back in forth between each other, if not actually forming one another).

Now, in relation to my initial reason for this thread, broad energy forms that can be seen as directly affecting one's environment would include the following: kinetic mechanical energy, thermal energy, radiant energy, and sound energy. It would also include electrical and magnetic energies; however, these two 'forms' of energy should really be understood as electromagnetic energy, as they cannot logically be separated from each other.*

The above list could be seen as ignoring the relationship between kinetic and potential types of energy as they oscillate between each other. However, I believe that the concept of different energy 'forms' should implicitly take this relationship into consideration, as one distinct form of energy wouldn't actually exist without interacting with another (as in the case of radiant energy, which is a back and forth between electrical and magnetic energy).

The separation of energy into different forms is important in order to be able to describe specific phenomenas (eg: light can be linked to radiant and thermal energy, even though it is indirectly connected to electromagnetic energy as well). Therefore, if I had a machine that could create/manifest light, which would be truly a work of sci-fi :tongue:, it would do so by manipulating various elements in order to direct radiant or thermal energy. A more complex example would be the Active Denial System, which works by directing radiant energy in order to produce very uncomfortable/painful burning sensations amongst living beings.

If any of the statements above are incorrect, feel free to correct me.

As a side note, I'd be interested to know more about the relationship between radiant and electromagnetic energy. From my experience, they are usually regarded as being entirely different? Is there any reason for this?

*While I did check various sources, I've derived most of the information concerning electric energy from the following website: http://amasci.com/miscon/energ1.html

PS: When I mentioned mass energy, it was indeed in relation to E=mc^2.

5. Apr 17, 2012

### haruspex

Not sure why leave gravitational (potential) energy out of the main list.
Think tides, rivers, hydro power, walking uphill...

Electrical and magnetic energy are separate though closely related. Your muscles operate by electrostatic attraction - no magnetism involved. Perhaps the best way to think of them is that it is particularly easy to convert between them.

Light is radiant energy is electromagnetic energy. No distinction. (But here I mean light generically, not just visible light. I assume you're aware that microwaves, radiowaves, infra red, visible, UV, gamma rays and X-rays are just different frequency ranges of light.) The term radiant might tend to be used more specifically in relation to radiant heat (i.e. infra red).

6. Apr 17, 2012

### davenn

or to put it another way .....

They are all photons with different energy levels :)

Dave

7. Apr 17, 2012

### Vernewells

Thanks Haruspex for the comment.

I did not include gravitational energy because, as far as I know, it is not a form of energy that can be directly manipulated/directed. However, I could be wrong. If there is any theoretical means that would permit one to directly manipulate gravitational energy (such as reducing the gravitational field in a specific area or directing gravitational waves towards a specific target), I would be most eager to hear about it.

In regards to electrical and magnetic energy, I’ll probably keep the two forms of energy separate from each other as they can indeed be used for different purposes.

My list would therefore consist of kinetic mechanical energy (such as motion), thermal energy, radiant energy, sound energy, electrical energy and magnetic energy.

8. Apr 17, 2012

### haruspex

Ever looked inside a longcase (i.e. "grandfather") clock? The descending weights power the mechanism. And I mentioned hydro power before. But I guess these don't lend themselves to large transfers of energy at lab-scale .
I should also point out mechanical energy (as distinct from kinetic energy) is represented by e.g. a wound spring.