Circuits and Electronics

1
Circuits and Electronics

• Midway in Chapter 2
• Resistor Combinations

2
Quick review

• Ohms Law V I R
• KVL
• Sv 0
• All Voltages in a Loop sum to Zero
• KCL
• Si 0
• All currents in a Node sum to Zero

3
Resistors in a Loop

• Letss say you have a loop with one voltage
  source and two resistors
• The voltage drop on the first resistor will be
  IR1 and the voltage drop on the second resistor
  will be IR2
• The total voltage Vt IR1 IR2
• Factor Vt I R1 R2

4
Results

• The Total of the Resistors in a loop, or in
  SERIES will be
• Rt R1 R2 R3 R4 .
• Therefore, the Current, I Vt /R1 R2
• Even farther, the total voltage, Vt, will divide
  over the two resistors

5
Now, lets look at the NODE

• Lets say you have three circuit branches coming
  into a node, and their other terminal ends at the
  same other node.
• One has a current source, and the other two
  branches are resistors.
• The voltage on each branch will be EQUAL.
• The total current I V\R1 R2 R3

6
Results

• The Resistances add in a loop - SERIES
• The resistance inverse add in a node Parallel
  configuration
• Even more, the division of voltage and current is
  proportional
• EXAMPLE PROBLEMS in our book are problems 2-13,
  2-14, 2-15