Voltage Divider

Discussion in 'Homework Help' started by Steve1992, May 7, 2006.

  1. Steve1992

    Thread Starter Senior Member

    Apr 7, 2006
    100
    0
    Vout = Vin x R2 / (R1 + R2)

    If Vin is 12V and I want Vout to be 4.5V

    What would the equation/math be to find the values for R2 and/or R1 if given.
    If R1 is given R2 would be a common factor?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    There is no unique solution. There must be some other condition. For example R1 + R2 must be 20K Ohms. Now there is a unique solution because you have two equations and two unknowns.
     
  3. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    Duplicate -- Delete
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    Duplicate -- Delete
     
  5. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    Duplicate -- Delete
     
  6. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    Duplicate -- Delete
     
  7. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    Duplicate - Delete
     
  8. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    Duplicate - Delete
     
  9. radiosmoke

    Member

    May 30, 2006
    17
    0

    Et = 12v

    you need to know the current. so use .1 amp arbitrarily.

    It = .1amp

    find R1 and R2

    by using Rt = Et/It or 12v/.1amps
    = 120ohms total resistance

    if you want 4.5 volts then R1 = 4.5v-12v = 7.5v drop
    7.5v / .1amps = 75 ohms = R1
    4.5v / .1amps = 45ohms = R2

    the same curent flows through both resistors. so that is used to find the total resistance

    and ratio is used to find voltage drops

    and resistances are in proportion to current.
     
Loading...