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Circuits and Electronics
Midway in Chapter 2
Resistor Combinations
Quick review
• Ohm’s 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
Resistors in a Loop
• Lets’s 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]
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
Now, lets look at the NODE
• Let’s 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 + …]
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