LESSON 6
SERIES-PARALLEL CIRCUITS
UNIT I
Block 3
Basic DC Circuits
EXPERIMENT
In this experiment, you will measure and calculate circuit values in series-parallel circuits.
Using the three series-parallel circuits on experiment card PC130-9A, you will perform the
following tasks:
 Measure equivalent and total resistances.
 Measure total current and then determine the equivalent resistance of the circuit.
 Measure current in the branches of a parallel circuit, confirming that the sum of the
branch currents equals the total current.
 Measure voltage drops across resistors in a series-parallel circuit to confirm that the
sum of the voltage drops in a series circuit equals the applied voltage across these
resistors.
 Compare measured values with calculated values and determine the percent error
between your measured and calculated values.
The experiment consists of two parts:
PART 1. PC130-9A CIRCUIT A
PART 2. PC130-9A CIRCUITS B AND C
EQUIPMENT REQUIRED
Test Console
PC130-9A
Multimeter
PREPARATION
Look at experiment card PC130-9A entitled Series-Parallel Circuits. Notice that PC130-9A
is very similar to experiment cards PC130-6A and PC130-8A that you previously used.
Are all resistors on PC130-9A carbon comp resistors?
Yes
No
Three circuits are mounted in PC130-9A: Circuits A, B, and C. PC130-9A also contains
five slide switches, S1 through S5, so you can measure current in the branches that
contain the switches. For the circuits to operate normally, close these switches by placing
them in the UP position. To measure current in a particular branch, place your current
meter leads across the switch in that branch. You then open the switch in that branch by
placing it in the DOWN position.
3-6-14
Copyright © 2002 by Nida Corporation
Block 3
Basic DC Circuits
PART 1.
UNIT I
LESSON 6
SERIES-PARALLEL CIRCUITS
PC130-9A CIRCUIT A
In Part 1, you will measure PC130-9A Circuit A current, voltage, and resistance. You will
also calculate the circuit values and then calculate the percent error between your
measured and calculated values.
Preparation
Look at the schematic diagram of PC130-9A Circuit A in Figure 17 and then look at Circuit
A on PC130-9A. Read the resistor values of Circuit A resistors R1, R2, and R3 and record
the values in Figure 17.
Figure 17. PC130-9A Circuit A
Part 1 Procedure
1-1. Set the test console POSITIVE and NEGATIVE SUPPLY controls to OFF.
1-2. Set PC130-9A switches: S1, S4, and S5 open (DOWN); S2 and S3 closed (UP).
1-3. Install PC130-9A carefully in the test console PC1 position.
1-4. Set your multimeter to read resistance. Measure the resistance Req of resistors R2
and R3 in parallel, from TP3 to TP6. Record your reading in Table 1 (MEASURED
VALUE).
1-5. Close PC130-9A switch S1 (UP).
1-6. Measure the total resistance RT of Circuit A from TP1 to TP6. Record your reading
in Table 1.
1-7. Apply power to the test console by turning the CONSOLE POWER switch to ON.
1-8. Adjust the POSITIVE SUPPLY power supply to +12 V. Record the applied voltage
value on Figure 17.
1-9. Turn the PC1 DC POWER switch to ON.
Copyright © 2002 by Nida Corporation
3-6-15
LESSON 6
SERIES-PARALLEL CIRCUITS
UNIT I
Block 3
Basic DC Circuits
1-10. Set your multimeter to read DC current.
Table 1. PC130-9A Circuit A
QUANTITY
MEASURED VALUE
CALCULATED VALUE
% ERROR
Req
RT
I2
I3
IT
ER1
ER2
1-11. Place your current meter test leads across S2, positive to TP4 and negative to TP6.
Open S2 (DOWN) and read current I2 through resistor R2. Record your reading in
Table 1 (MEASURED VALUE).
1-12. Next, place your current meter across S3. Then close S2 (UP) and open S3
(DOWN). Read current I3 and record your reading in Table 1.
1-13. Next, place your current meter across S1. Then close S3 (UP) and open S1
(DOWN). Read total current IT and record your reading in Table 1.
1-14. Close S1 and set your multimeter to read DC voltage.
1-15. Read the voltage drop across resistor R1, TP1 to TP2. Record your reading in
Table 1 (MEASURED VALUE).
1-16. Read the voltage drop across R2, TP3 to TP6 and record your reading.
Notice that the voltage reading across R2 is the same as that across R3. This is
because R2 and R3 are in parallel, so TP4, TP5, and TP6 are all at the same
potential. Move your test leads from TP4 to TP5 and then to TP6 and read the
voltage drops.
Are all three readings the same?
Yes
No
1-17. You have completed the measurements. Turn the PC1 DC POWER switch to OFF.
1-18. Using the resistor values you recorded on the circuit in Figure 17, calculate the
value for each Circuit A Table 1 QUANTITY. Remember that Ea=12 V. Record
your answers in Table 1 (CALCULATED VALUE).
1-19. Calculate the percent error between your measured and calculated values in Table 1.
Record your answers in Table 1 (% ERROR).
3-6-16
Copyright © 2002 by Nida Corporation
Block 3
Basic DC Circuits
PART 2.
UNIT I
LESSON 6
SERIES-PARALLEL CIRCUITS
PC130-9A CIRCUITS B AND C
In Part 2, you will measure current and voltage drops on PC130-9A Circuits B and C.
Next, you will determine the equivalent resistance in each circuit and then calculate circuit
values. You will also calculate the percent error between your measured and calculated
values.
Preparation
First look at the schematic diagram of PC130-9A Circuits B and C in Figure 18. Then look
at Circuits B and C on PC130-9A. Notice that Circuits B and C are series-parallel circuits
which are connected in parallel, forming yet another series-parallel circuit. Read the values
of the resistors in both circuits and record the values in the blanks provided in Figure 18.
Figure 18. PC130-9A Circuits B and C
Part 2 Procedure
2-1. Check that the test console control settings are the same as they were for the
Part 1 Procedure. This means the test CONSOLE POWER switch is ON, the
POSITIVE SUPPLY is set to +12 V, and the PC1 DC POWER switch is OFF.
2-2. Open PC130-9A S1, S2, and S3, since you will not be using Circuit A; close S4 and
S5.
2-3. Turn the PC1 DC POWER switch to ON. The test console VOLTMETER should read
+12 V.
2-4. Set your multimeter to read DC current and place your test leads across S4. Open
S4 and read Circuit B current IB. Record your reading in Table 2 (MEASURED
VALUE).
2-5. Close S4 and place your test leads across S5. Open S5 and measure the Circuit C
current IC. Record your reading in Table 2.
Copyright © 2002 by Nida Corporation
3-6-17
LESSON 6
SERIES-PARALLEL CIRCUITS
UNIT I
Block 3
Basic DC Circuits
2-6. Now add your measured values for IB and IC (since IT = IB + IC). Record your
answer for the value of IT in Table 2.
Table 2. PC130-9A Circuits B and C
QUANTITY
MEASURED VALUE
CALCULATED VALUE
% ERROR
IB
IC
IT = IB + IC
ER5
ER6
ER7
ER8
2-7. Close S5 and set multimeter to read DC voltage.
2-8. Measure the voltage drop ER5 across parallel resistors R4 and R5. Record your
reading in Table 2.
2-9. Measure the voltage drop ER6 across R6 and record your reading.
2-10. Measure the voltage drop ER7 across R7 and record your reading.
2-11. Measure the voltage drop ER8 across parallel resistors R8 and R9 and record your
reading.
2-12. This completes the measurements. Remove the multimeter leads and turn your
multimeter OFF. Return the test console POSITIVE and NEGATIVE SUPPLY controls
to OFF, and turn the CONSOLE POWER switch to OFF. Remove PC130-9A from
the test console. Return all equipment to its assigned storage place.
2-13. Using the resistor values you recorded on the circuit in Figure 18, calculate the
value for each Circuit B and C Table 2 QUANTITY. Remember that Ea=12 V.
Record your answers in Table 2 (CALCULATED VALUE).
HINT
First calculate the equivalent resistances, then the currents,
and then the voltage drops.
2-14. Compare your measured and calculated values by calculating the percent error.
Record your answers in Table 2 (% ERROR).
3-6-18
Copyright © 2002 by Nida Corporation