Electronics Forums > thevenin's help

 Thread Tools Display Modes

# thevenin's help

Junior Member
Join Date: Jan 2012
Posts: 1

 01-27-2012, 09:01 PM
ok i have been given this as a part of my electonics assignment, ive spent ages pondering on it and have got nowhere. help would be greatly appreciated
Attached Thumbnails

Senior Member
Join Date: Apr 2010
Location: Tombstone, Arizona
Posts: 539

 01-28-2012, 02:47 AM
Thévenin's theorem for linear electrical networks states that any combination of voltage sources, current sources, and resistors with two terminals is electrically equivalent to a single voltage source and a single series resistor. The single voltage source is the open circuit voltage (no load) at the two terminals. The single series resistor is the resistance looking back into the network from the two terminals with all the sources zeroed, i.e., voltage sources are shorted while current sources are opened.

So your circuit has four terminals: 0, 1, 2, 3. Which two will you choose to be the terminals of your Thévenin equivalent network?

Junior Member
Join Date: Mar 2010
Posts: 6

 01-30-2012, 06:47 AM
I see it rather simply. The left and center resistors can be combined to a single series resistor equal to their parallel combination, excited by an AC source equal to the dividing ratio. Now you have a single source and a single resistor. So you have 6.67 Ohms in series with 33.33V source.

That is loaded by the 20 Ohms in series with the inductor. So you have, if you combine parts, 33.33 V in series with 26.67 Ohms and the inductor. Now with only a source, a resistor, and an inductor, you can compute the current.

Senior Member
Join Date: Apr 2010
Posts: 1,264

 01-30-2012, 12:30 PM
Quote:
 The left and center resistors can be combined to a single series resistor equal to their parallel combination
what? How can two resistors in series be equal to their parallel equivalent?

Super Moderator
Join Date: Nov 2011
Location: Germany
Posts: 2,191

 01-30-2012, 12:37 PM
Yes they can. Think of V1, R1 and R3 as a single voltage source with an equivalent output resistance given by the parallel connection of R1 and R3 AND you'll have to consider the reduced output voltage which is V1 divided by the voltage divider R1/R3.
If you do the math, it comes out the same.

Harald

Senior Member
Join Date: Apr 2010
Posts: 1,264

 01-30-2012, 12:47 PM
Guess I will have to go back and re-read thevenin's theorem again. Because I am now lost on what I thought I knew. *shrugs*

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post ChrisM1111 Electronic Repair 0 02-23-2004 02:30 PM Dana Raymond, a minor God Electronic Basics 1 08-07-2003 08:44 PM st Electronic Basics 0 08-06-2003 06:28 PM