Experiment 16: Series and Parallel Circuits

Experiment 16: Series and Parallel Circuits

Figure 16.1: Series Circuit

Figure 16.2: Parallel Circuit 1

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Experiment 16: Series and Parallel Circuits

EQUIPMENT

Universal Circuit Board (2) 100- Resistors (2) 200- Resistors (2) 300- Resistors (2) Digital Multi-Meters Power Supply (5) Jumpers (6) Wire Leads

Figure 16.3: Combination Circuit

Experiment 16: Series and Parallel Circuits

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Advance Reading

Text: Resistors in series, parallel, combination.

Objective

The objective of this lab is to study circuits with resistors connected in series, parallel, and combination.

Theory

In the previous experiment, you constructed 4 circuits, each circuit built with one resistive element. In this experiment, you will construct circuits using multiple resistors.

The first type of circuit you will construct is a series circuit (Fig. 16.1 and Fig. 16.4). In a series circuit, the resistors are connected end-to-end such that the current is the same through each resistor: The current has only one path available. The voltage drop across each resistor depends on the resistor value.

For a series circuit, the total equivalent resistance, Req is:

N Req = R1 + R2 + R3 + ? ? ? + RN = Ri

i=1

(Resistors in Series)

(16.1)

For a parallel circuit, the total equivalent resistance, Req, is:

1 Req

=

1 R1

+

1 R2

+

1 R3

+???+

1 RN

=

N

i=1

1 Ri

(16.2)

(Resistors in Parallel)

Figure 16.5: Parallel Circuit Schematic

The third type of circuit you will construct is a combination circuit (Fig. 16.3 and Fig. 16.6). Resistive elements are not connected in series or parallel. To calculate the total equivalent resistance of a combination circuit, it should first be simplified (reduced to an equivalent resistor, Req). This is done by choosing resistors that are connected in either series or parallel, one step at a time, adding those elements by use of Eq. 16.1 or Eq. 16.2, then proceeding to the next set of elements.

Figure 16.4: Series Circuit Schematic

The second type of circuit you will construct is a parallel circuit (Fig. 16.2 and Fig. 16.5). Resistors are said to be in parallel when they are connected to each other at each end. In this way, the potential difference applied across the combination is the same as the potential difference applied across an individual resistor. The current through each resistor depends on the resistor value. The current has more than one path available and takes all available paths.

Figure 16.6: Combination Circuit Schematic

Note that it is not correct to, for example, calculate the resistance of the 3 resistors across the top of the circuit using Eq. 16.1, and then calculate the resistance of R4, R5, and R6 using Eq. 16.2. You must identify which resistors are either in parallel or in series, then apply the appropriate equation one step at a time.

4 Name: 1. What is a series circuit? (10 pts)

Prelab 16: Series and Parallel Circuits

2. What is a parallel circuit? (10 pts)

3. Is the equivalent resistance, Req, of a series circuit greater than or less than any individual resistor? (10 pts)

4. Is the equivalent resistance, Req, of a parallel circuit greater than or less than any individual resistor? (10 pts)

5. Calculate Req for each of the first three circuits shown in Fig. 16.4 - Fig. 16.6 using the stated nominal values for resistance. (Show all work on back of this sheet.) (25 pts)

6. You will plot I vs. V for each of the three circuits on one graph. What value should each slope have (use the stated values for resistance)? (25 pts)

7. Create Data Tables in your lab notebook for all parts of this experiment. Sketch the column headings on the back of this sheet. (10 pts)

Name:

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Section:

Date:

Datasheet - Exp 16: Series and Parallel Circuits

PROCEDURE

Part 1: Series Circuit

Record all data in tables on next page.

Recall that (i = 1, 2, . . . , n) 1. Measure each Ri, then construct a series circuit

(Fig. 16.4) with 100-, 200-, and 300- resistors and ammeter (200 mA DCA); do not connect the power supply yet.

Fig. 16.4

2. Draw the schematic using measured Ri Values.

3. Calculate Reqfor the circuit.

4. Measure Reqby plugging an ohmmeter in place of the power supply.

5. Remove the ohmmeter and connect the unplugged power supply and a voltmeter (DCV) to your circuit.

Get instructor approval of your circuit

6. Always be sure the power supply is turned off before you plug it into an outlet. Plug in the power supply, and set the voltage to 1.00 V. Measure the current and voltage.

7. Record the current (A) and the voltage (V) as you increase the voltage in 1.0 V increments up to 4.0 V.

8. Leave the voltage at 4.0 V; disconnect the voltmeter

from the power supply. Maintaining the same orien-

tation of the leads (if clockwise, black follows red),

measure Vi, the voltage drop across each resistor.

9. Add these potential differences (

i=1 Vi).

10. Does i=1 Vi equal -4.0 V? If not, ask your TA for

guidance.

Part 2: Parallel Circuit

11. Repeat Part 1, Step 1 - Step 8, for the parallel circuit (Fig. 16.5).

Fig. 16.5 Things to consider when writing your report: Does V2 = V1 + VA, or does V2 = V1 = V3? Are each of these values negative or positive?! Yes, it matters! Does V = |V1 + VA|? Part 3: Combination Circuit

12. Repeat Part 1, Step 1 - Step 8, for the combination circuit (Fig. 16.6).

Part 4: Graphing

Fig. 16.6

13. Graph I vs. V for each of the first three circuits (Part 1, Part 2, and Part 3 ).

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