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Homework Help: Battery and U

  1. Nov 4, 2015 #1
    1. The problem statement, all variables and given/known data
    (My english is not good)

    If I have a battery that is 4v why isnt U = 4 ?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Nov 4, 2015 #2


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    What is U?
  4. Nov 4, 2015 #3
    U=RI I dont know what it is called in english
  5. Nov 4, 2015 #4


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    Your question is not clear. Are you saying the battery is connected to a resistor of value R and a current of value I is flowing through it? Please make your question clearer.
  6. Nov 4, 2015 #5
  7. Nov 4, 2015 #6


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    The voltage of the battery will be equal to I x R. Why do you think it is not?
  8. Nov 4, 2015 #7


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    What you are calling 'U' appears to be a lower case 'v'. In any event, 'v' is called the 'voltage' in English.

    V = I R is the mathematical statement of Ohm's Law.
  9. Nov 5, 2015 #8
    Becouse the voltage U gets divided between the resistors and so if you have two resistors and 4 volts battery, the voltage gets divided between the two resistors. And so you can have 2volts on one resistor and 2 on the other. Or 3 on one resistor and 1 on the other. It depends entirely on the resistances values.
    Last edited by a moderator: Nov 5, 2015
  10. Nov 5, 2015 #9
    lets say i have this:
    I dont now exactly what voltage is. I have tried to google it and i have watched lots of videos. All of them say: think of it this way "how bad do the electron want to move". Is the volt same befpre and after a resistor?
  11. Nov 5, 2015 #10


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  12. Nov 5, 2015 #11
    But what is U? I dont understand what it is. The only thing I see is a letter not what it actakly is
  13. Nov 5, 2015 #12
    What voltage is: Imagine 2 atoms divided by a distance. Atom A and atom B. Atom A looses some of the electrons therefore it becomes more positive(the positive charge of the protons becomes less compensated). Its electric field becomes stronger. Now you should know that every atom has a positive core and that core uses electric field to attract electrons in. However, since both atoms before were in equilibrium and now suddently A looses electrons it field grows and the equilibrium is broken. In order to restore it, A will attract some of the electrons from B until both atoms have the same positive charge. At that point equilibrium is restored and every single electron who left B will make it more positive than A and B will attract it back. ! Take in mind that i use single atoms in my argumentation. In battery is the same but there are billions of atoms more. So Voltage is the work done by the electric field to move an electron from (in this case) B to A. Also B may be 3volts and A6volts. There still will be potential difference of 3volts between them and current will still flow. What happens is that A becomes less positive as it is accepting electrons and B becomes more positive becouse it is giving away electrons leaving behind more uncompensated positive charge. Current will flow until A and B has the same voltage: A-6,5,4 5volts B-3,4,4.5volts. The voltage between this two points is given by V=VA-VB. Does this helped you, let me know. Also you can see Atom steucture in internet
  14. Nov 5, 2015 #13
    Also current I is a flow of electrons in one dirrection coused by a potential difference between 2points (in our case A and B). Voltage is also called potential. The faster the electrons the bigger is the heat and light and magnetic field generated. The bigger the potential difference- the bigger will be the atttaction force on these electrons and faster they will be.
  15. Nov 5, 2015 #14
    And U is the EU version of V. Both are Voltage
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