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A Practical Exercise Name:________________ Section: ____________ I. Purpose.
- Review the construction of a DC series circuit on a quad board from a circuit schematic.
- Review the application of Kirchhoff’s Voltage Law in the analysis of a DC series circuit.
- Review the calculation of real, supplied and dissipated power in a DC series circuit.
- Introduce the calculation of total resistance of multiple resistive elements connected in series.
- Introduce the application of the Voltage Divider Rule in the analysis of a DC series circuit.
- Introduce the concept of circuit ground and connecting different points of the same circuit to the circuit ground.
- Introduce the concept of voltage subscripts and the measurement of the voltage as designated by its subscript.
- Introduce the simplification of voltage sources to point sources in a circuit. II. Equipment. Keysight 34450A Digital Multi Meter (DMM) Agilent E3620A Dual DC Power Supply 560 - Ω, 2 20 - Ω, and 1000 - Ω resistors III. Pre-lab calculations. Show all work. Step One: In the space below, draw the equivalent conventional closed loop circuit schematic of the DC series circuit of Figure 1. Do not simplify by combining the resistors. Figure 1 Figure 2 Step Two: Calculate total current. □ Calculate the total resistance of the circuit.
RTOT = _____________
□ Use Ohm’s Law to predict the total current in the circuit.
ITOT = _____________
+ 12 V
Step Three: Predict DC voltage values. □ Use the Voltage Divider Rule to calculate the voltage drop across each resistor. VX = (RX / RT) E; VX is the voltage across RX, RT is the total resistance of series resistors, and E is the total applied voltage.
V 1000 Ω = _____________
V560Ω = _____________
V220Ω = _____________
Step Four: Instructor or lab assistant verification that pre-lab calculations are complete. ______________________________ IV. Lab Procedure. Time Required: 50 minutes. Check-off each step as you complete it. Step One: Measure actual resistor values. □ Using your DMM, measure and record the actual resistance of the 1000 - Ω resistor, the 560-Ω resistor and the 220-Ω resistor. R1000Ω = _______________ R560Ω = _______________ R220Ω = _______________ Are these measured values of resistance within allowed tolerances? Yes__________ No_________ □ Calculate the total resistance of this DC series circuit based on your measured resistor values. RTOT = _______________ How does this value of resistance compare to the value calculated in the pre-lab calculations section? **Exact__________ Very close__________ Very Different_________ Why is it important to check actual resistance values instead of relying on nominal values? How will this difference affect your measured current and voltage values?
__________________________________________________________________________________**
T T T 1000 Ohm T 220 Ohm Es = 12 Volts 560 Ohm a b d (^) c **Explain any differences
__________________________________________________________________________________**
□ Using your measured voltage drops, verify Kirchhoff’s Voltage Law in this closed loop DC
series circuit (number substitution and calculations are required).
Σ Egains = Σ Vdrops
Σ _____________= Σ_________________________________________________
How closely does the sum of the DC voltage gains match the sum of the DC voltage drops? Exact__________ Very close__________ Very Different_________ If not “Very Close” or “Exact”, then you need to determine why and fix your circuit. Step Four: Voltage Subscripts. Single subscript voltages designate the voltage potential difference between some point with respect to the circuit’s ground. Va can be measured by connecting the DMM red lead to point a and the DMM black lead to the ground (point d ). Figure 3
□ Use the DMM to measure the voltages at these single-subscript points.
Va = _____________
Vb = _____________
Vc = _____________
Vd = _____________
Vab Va Vb
Double subscript represents the voltage difference between single subscripts. It can be calculated if you know the Single Subscript voltages. Vbc = Vb – Vc Vcb = Vc – Vb. □ Using these measured single-subscript voltage values, predict the double-subscript voltage values below.
Vab = _____________
Vbc = _____________
Vcb = _____________
Vdb = _____________
Double subscript voltages designate the voltage potential difference between two points. Place the DMM red lead (“Input HI”) on the first subscript node, and the black lead (“Input LO”) on the second subscript node. Vab can be measured by placing the DMM red lead on point a and the DMM black lead on point b. □ Use the DMM to measure the double-subscript voltages below.
Vab = _____________
Vbc = _____________
Vcb = _____________
Vdb = _____________
How closely do the measured double-subscript values match the predicted values? Exact__________ Very close__________ Very Different_________ If not “Very Close” or “Exact”, then you need to determine why and fix your circuit.
