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

Electric current and voltage question

  1. Apr 7, 2009 #1
    I'm trying to clear up my picture of basic electricity and electronics. I've looked at some other posts that ask what is voltage, but have come away with questions in my mind. Here are some thoughts I'm throwing out there in the area of current energy, speed, and force.

    I feel there are some principles and factors that aren't acknowledged when I study this area.
    Does resistence to a current affect the quantity and speed of the electrons passing a point?
    How does the speed and quantity of the current affect the output into appliances and its uses/how is this characteristic utilised? (voltage might resolve this question)
    Where is the offload of energy by a current into an appliance and output, so it returns to complete the circuit carrying with it less energy? It is never explained like that.
    Why don’t we see a difference in speed after an electric current has entered something and exits to complete the circuit or/and do the electrons slow down as they go through a resistor, coming out the other end slower? I have seen simulators that suggest otherwise. Why does a current come out of an appliance and resister the same speed as it went in, shouldn’t some energy be used? This is never written beside circuit diagrams and explanations.

    Is it an issue of force applied, why aren't watts and connection to the concept of power used more often? Is this where e.m.f occurs in a way similar to Newton mechanics, force applied with a resulting speed depending on the mass, thus in electricity the effect of some input force has varying results on the amount of resulting current and speed. I don't find this kind of breakdown and wording.

    Perhaps some of my wording of these particular points is unconventional. Dare I say it but I feel there are gaps in the language and explanations of the foundations of electricity from the ones that I've seen. I feel a lot of this has to do with ohms law, voltage, e.m.f. and potential difference and I've read definitions of all these things and feel I have a decent understanding, but can anyone help clear up some of the points I've raised, or suggest some good material or tutorial that addresses this better.

    Thanks for reading my post.
     
    Last edited: Apr 7, 2009
  2. jcsd
  3. Apr 7, 2009 #2
    Trying to learn basics here is going to result in a barrage of information betting thrown at you. Some is good, and some is bad. If you are a beginner, you won't know which is which.

    Enroll in university courses and study math, physics, chemistry, electric circuit theory, etc.

    Or, if that doesn't appeal to you, go to a university library and read some good university-approved, peer-reviewed textbooks on the above subjects. It will take years to learn. In my mind, why spend hundreds or thousands of hours studying unless you receive college credit?

    This subject is a profession which takes a lifetime to master. Take advice from people who have vast experience in the field doing R&D, and publishing papers, receiving patents, etc. These forums provide information dispersed among tons of mis-information. You've got to be careful.

    Does this help?

    Claude
     
  4. Apr 8, 2009 #3
  5. Apr 8, 2009 #4
    Okay I know its a long post and I am weary of receiving information I can get easily somewhere else. Which is why I have spent some time studying this area and if you've read my thread carefully I'm saying that I think there are ideas and concepts that education in this area often overlooks. Its how I would think about circuits but it doesn't word it the same way. Having read about the area I raise specific points.

    I appreciate your feedback in the reply. I agree when you try to filter out those who haven't tried to understand this area, but I have. I also believe one shouldn't have to go college to gain an understanding of this area, I respect that discoveries in this field are a result of experimentation, thorough work and reasoning. But the points I've raised aren't too abstract and to me surely obvious questions, there shouldn't be so much ambiguity over the subject.

    I realise a forum has a difficult job in trying to surgically isolate the problem/confusion and resolve it, but I think it is up to it. A forum is here so that one can interact with what they've learned, trying to know the conclusions and picture experts have created on this area. Because you couldn't answer these questions could mean you're slightly unsure of the details of circuits too so is surely worth a discussion.

    Further points;
    Potential difference and voltage are probably the root of many of these other questions. I've seen the hydraulic analogy put it isn't complete.

    On the question of why don’t the electrons slow down as they go through a resistor, coming out the other end slower? I refer to a resister simulator in ohms law on this page http://falstad.com/circuit/e-index.html, this doesn't explain how it works.

    I have seen all about circuits. com and it is a good website but doesn't answer the points I've raised. If I can't get answers here maybe their forum may be more suitable.
     
  6. Apr 8, 2009 #5
    As far as the educational system overlooking key concepts, what gives you that idea? Please be specific, giving 3 examples. The educational curriculum cannot teach everything in 4-5 yrs. Some simplifications have to be made. Then the student can explore further in detail the subject they wish to get deeply involved in.

    As far as one not needing to go to college to understand electronics, my reply is that outside of college, one can only acquire a very limited grasp of the basics. Outside of college, one will also attain some bad habits, beliefs, misconceptions, false assumptions, etc.

    Potential difference / voltage are NOT the root of electrical science. CHARGE IS the ROOT. Current and voltage are both defined in terms of charge, as well as time and energy. You start with charge, and build from there.

    I won't steer you wrong. There are no shortcuts in life. To be a star in any field requires years of hard work, as well as natural ability. Neither one alone is sufficient. I've met EE's and EE hopefuls who have the talent but not the work ethic and vice-versa. Both are needed.

    Anyone who tells you that any person can understand electronics w/o having to go to college is leading you astray.

    Claude
     
  7. Apr 8, 2009 #6
    Oh look what I meant by the college thing was that one shouldn't have to study for 4 years to get an informed low level understanding of a subject, like one might be curious about DNA that shouldn't mean it takes 4 years to get an idea of what its all about. Of course I realise to be become an expert in the field may require a college degree. Anyway before I go away empty handed can anyone answer why a resister doesn't seem to affect a current? Any thoughts on any of the other points raised are welcome as well.
     
  8. Apr 8, 2009 #7
    The resistor can be examined at the macro as well as micro level. If you have no college background then the macro level would probably be a good place to start.

    But to understand what happens at the atomic level requires the micro point of view. This is solid state physics. To understand the energy associated with electrons changing quantum levels and moving between valence and conduction bands involves statistical thermodynamics and quantum mechanics. Have you had a lot of chemistry and physics?

    You're asking for beginner help but the question is quite advanced. Let me summarize with this. The late Richard Feynman (1919-1988), one of the greatest physicists in modern times, often stated that neither he nor anyone alive really understands quantum mechanics (QM). QM is one of those things I make it a point not to think about because it drives me crazy. How can an electron only occupy certain discrete energy levels? All I can do is accept what the scientific community has observed and published. I cannot explain or understand it. No one understands QM fully. We just accept it.

    Have I helped?

    Claude
     
  9. Apr 8, 2009 #8
    No I didn't want to bring the micro QM world into it, just a macro level, so no that didn't really help to answer your question. If I wanted to know what happened on the micro I would have asked for it but thanks anyway for the response.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Electric current and voltage question
Loading...