Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Energy and charge

  1. Feb 26, 2006 #1
    I know this might seem very simplistic to some so don't bash or flame me, as I just want to learn. How exactly is energy made, or transfered, and what gives it the instruction to transfer? Is energy matterless or massless? I've used it in physics in equations and I know it is measured in joules, I just want to know the fundamentals and underlying concepts of it. I know the conservation of energy says that it cannot be created nor destroyed, but exactly where did it come from? If energy is massless does that mean that time doesn't exist for it? That it has been here since the beginning of the universe, just pushed around like a person frozen in a block of ice? Is energy only given off as a photon, and is limited only in the electromagnetic spectrum? Or is there energy present in gravity or weak or strong force?
    Are charge and energy one in the same? Because I'm fuzzy on both ideas on voltage (energy) and current (charge). Is the energy in voltage like the energy from visible light?
  2. jcsd
  3. Feb 26, 2006 #2

    Claude Bile

    User Avatar
    Science Advisor

    Energy is defined as 'the ability to do work', which pretty says energy is energy and is not very enlightning. Fundamental concepts such as energy cannot be explained on a more fundamental level, because they are, themselves fundamental concepts.

    Having said that, I can answer some of your questions regarding the properties of energy.

    - I'm not 100% sure what you mean by instruction, I assume you mean what tells energy to change into what form and when? If that is your question, then the ultra-short answer would be force.

    - Energy is massless and matterless in general, however mass is a form of energy.......

    - Where did energy come from? That would be a question for an astrophysicist, but it is worth remarking that the net energy in our universe is zero if you include the negative contributions from the various fields (from what I remember, I could be wrong on this).

    - I'm not sure what you mean as to whether time exists for energy or not.

    - Energy transmission is certainly not limited to electromagnetic fields, or indeed any of the fundamental fields. Consider the case of pressure waves (i.e. sound waves).

    - Charge and energy are seperate quantities. Voltage, which is closely related to charge, is a specific type of energy, namely electrical potential energy. The units eV are sometimes used to describe photon energy, particularly in optoelectronic devices.

  4. Feb 26, 2006 #3
    Thanks for the replies. Does all forms of energy move at the speed of light? So since it is massless and moves at the speed of light wouldn't that mean in general relativity that time stops for energy? Mass is a form of energy? But in the equation E=mc^2 is energy equals energy times the speed of light squared? Each force releases its own type of energy, and each force has its own particle? So with for example - gravity, everything is attracted into the center which creates heat, light, and other forms of energy or is that multiple forces working together, producing their own type of energy; if forces give the instruction to produce only certain types of energy? If I understood in chemistry an electron gets excited and moves to a higher valence orbital (by a force?). The distance the electron traveled is the amount of energy it will release when it returns to the lower orbital? How is the energy created because one force - strong force which keeps the nucleus intact - and another force electomagnetic force (which keeps the atoms together because of charges?) keep the atom together. There has to be an outside force that excites the electron? But it can't be electromagnetic or strong force to my understanding, so it leaves gravity and the weak force?
  5. Feb 27, 2006 #4

    Claude Bile

    User Avatar
    Science Advisor

    I will try to answer your questions (in order) as best I can.

    - Not all forms of energy travel at the speed of light, in fact, very few do.
    - Energy is not massless, mass in this context is an inertial mass, not the physical presence of matter.
    - Be careful here, do you mean mass or matter? Matter is a form of energy, but the relationship between energy and mass is stronger. E = mc^2 tells us that energy and mass are equivalent, that is, energy is mass (i.e. it posesses inertia) and mass can be used to do work (since it is energy).
    - I am unclear as to what you mean by force releasing energy.
    - Each fundamental force has its own force transmitting virtual particles.
    For example, the force transmitting particle for gravity is the graviton, for the strong nuclear force it is the gluon.
    - I'm not really following the next question, but I will remark that the distinction between different types of force and energy is purely a man-made one. An electron does not care what force is being applied to it, a force is a force and it will act accordingly. What dictates what form energy is converted to and when by and large depends on the force you apply to it.
    - Electrons can be excited to a higher orbital in a variety of ways, through photon absorption, electrical excitation and so on, but all the possible ways I can think of involve electromagnetic forces. There is no relationship between the energy of an orbital and its distance from the nucleus. Why does the fact that the atom is held together via electromagnetic forces prohibit a second electromagnetic force from acting on the atom?

  6. Feb 27, 2006 #5


    User Avatar

    -Each fundamental force uses the same energy. Energy is energy, its the forces that are different, and forms of energy that are different.
    -A consequence of gravitational attraction is sometimes heat and light being released, but but again, energy is energy, its energy in different forms that you're talking about. Forces don't give instruction to produce different types of energy.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook