Why is Electrical length greater than physical length?

Discussion in 'General Electronics Chat' started by shopitham, Feb 14, 2011.

  1. shopitham

    shopitham

    Joined:
    Nov 30, 2010
    Messages:
    5
    HTML:
    Hai
    1)What does a electrical length in transmission line means?
    2)How does it differ from the physical length?
    3)Why is electrical greater than that of the physical length?
    some pls help me find the ans .
    
    Thanks
    Shofiya
    
     
    shopitham, Feb 14, 2011
    #1
    1. Advertising

  2. shopitham

    rob_croxford VIP Member

    Joined:
    Aug 3, 2010
    Messages:
    262
    The Physical length of a coaxial cable (such as cable used in transmission lines) is the length from one end of the connector to the other.

    The ELECTRICAL length of such a cable depends on the size and type of the dialectric material used within it (if im not mistaken). It is measured at the mating plane of the outer conductor and is the length of the adapter as it appears to the signal traveling through it.

    Try google if u need more info.

    Rob
     
    rob_croxford, Feb 14, 2011
    #2
    1. Advertising

  3. shopitham

    davenn Moderator

    Joined:
    Sep 5, 2009
    Messages:
    6,647
    The electrical length of a transmission line is dependant on 2 things...

    1 ... the velocity factor of the line and
    2 ... the frequency
    an example ... to find the electrical length of a transmission line or dipole antenna
    say for 400MHz

    (300 million metres / sec (300,000 km / sec))
    300 / 400MHz = 0.75m or 75cm that is the wavelength
    now if we want an electrical wavelength in a transmission line that has a VF (velocity Factor) of 0.85 then....

    75 x 0.85 = 63.75 cm so you can see that the electrical wavelength is shorter
    than the free space wavelength

    Dave

    Dave
     
    davenn, Feb 14, 2011
    #3
  4. shopitham

    ans

    Joined:
    Nov 25, 2010
    Messages:
    19
    Nice information thanks for sharing.
     
    ans, Feb 16, 2011
    #4
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. LIJO
    Replies:
    1
    Views:
    357
    Kevin G. Rhoads
    Aug 21, 2003
  2. LIJO
    Replies:
    2
    Views:
    1,335
    Kevin G. Rhoads
    Aug 21, 2003
  3. Paco Rosso

    Refelctions greater than 1 and L*

    Paco Rosso, Aug 1, 2005, in forum: Lighting
    Replies:
    1
    Views:
    218
    Paco Rosso
    Aug 2, 2005
  4. john54

    Can aperture efficiency of antenna be greater than 100%?

    john54, Jun 14, 2012, in forum: General Electronics Chat
    Replies:
    0
    Views:
    284
    john54
    Jun 14, 2012
  5. 24Volts
    Replies:
    5
    Views:
    309
    24Volts
    Aug 17, 2013
Loading...

Share This Page