# Voltage Divider

## Chapter 3 - DC Circuits

PARTS AND MATERIALS
• Calculator (or pencil and paper for doing arithmetic)
• 6-volt battery
• Assortment of resistors between 1 KΩ and 100 kΩ in value
I’m purposely restricting the resistance values between 1 kΩ and 100 kΩ for the sake of obtaining accurate voltage and current readings with your meter. With very low resistance values, the internal resistance of the ammeter has a significant impact on measurement accuracy. Very high resistance values may cause problems for voltage measurement, the internal resistance of the voltmeter substantially changing circuit resistance when it is connected in parallel with a high-value resistor. CROSS-REFERENCES Lessons In Electric Circuits, Volume 1, chapter 6: “Divider Circuits and Kirchhoff’s Laws” LEARNING OBJECTIVES
• Voltmeter use
• Ammeter use
• Ohmmeter use
• Use of Ohm’s Law
• Use of Kirchhoff’s Voltage Law (“KVL”)
• Voltage divider design
Voltage divider
v1 3 0
r1 3 2 5k
r2 2 1 3k
r3 1 0 2k
.dc v1 6 6 1 * Voltages around 0-1-2-3-0 loop algebraically add to zero:
.print dc v(1,0) v(2,1) v(3,2) v(0,3) * Voltages around 1-2-3-1 loop algebraically add to zero:
.print dc v(2,1) v(3,2) v(1,3)
.end

This computer simulation is based on the point numbers shown in the previous diagrams for illustrating Kirchhoff’s Voltage Law (points 0 through 3). Resistor values were chosen to provide 50%, 30%, and 20% proportions of total voltage across R1, R2, and R3, respectively. Feel free to modify the voltage source value (in the “.dc” line, shown here as 6 volts), and/or the resistor values. When run, SPICE will print a line of text containing four voltage figures, then another line of text containing three voltage figures, along with lots of other text lines describing the analysis process. Add the voltage figures in each line to see that the sum is zero.
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