Basic Elec. Engr Basic Elec. Engr. Lab . Lab ECS 204 ECS 204 - PowerPoint PPT Presentation

Basic Elec. Engr Basic Elec. Engr. Lab . Lab ECS 204 ECS 204 Asst. Prof. Dr. Prapun Suksompong prapun@siit.tu.ac.th Thevenin’s and Norton’s Theorems • Lab 2 New toy: Potentiometer • Building a “fake” current source • 1

Lab 2: Circuit under consideration Direct measurement of I L (A.4) 2

Outline of the lab Part A (Thevenin Eq.) Load resistor Part B (Norton Eq.) 3

Part A: Thevenin Equivalent (1) Part A voltage divider R  3 (A.12) V V   TH ps R R R 1 2 3   (A.13)   / / R R R R 3 1 2 TH V  (A.14) TH I  L R R TH L 4

Part A: Thevenin Equivalent (2) Part A Directly measure V TH (A.5) and R TH (A.8) deactivated Source(s)  V Build (Thevenin) equivalent circuit to measure I L (A.11) 5

Part B: Norton Equivalent (1)  R R N TH V  (B.6) ps I  N R R 1 2 R  N (B.7) I I  L N R R L N Part B 6

Part B: Norton Equivalent (2) Note that the ammeter itself acts as a short A circuit. Directly measure I N (B.2) Build (Norton) equivalent circuit to measure I L (B.5) Part B 7

Lab 2: Summary Part A (A.14) (A.11) (A.4) (B.7) Part B (B.5) 8

Need resistor whose value can be Lab 2: Summary adjusted arbitrarily Part A (A.14) (A.11) (A.4) (B.7) Need current source Part B (B.5) 9

Potentiometer (Pot) 10

Pot as a variable resistor  Manually adjustable resistor  Three terminals  The resistance between the middle terminal and either of the two sides depends on the position of the wiper. 11

A Current source I S V PS  We do not have current source.  Again, it is meaningless to connect an ammeter directly across the power supply. This will NOT give you the amount of current produced by the power supply.  We use a voltage source (power supply) to give the specified amount of current. I N pot 13