Download lab 6 electrical circuits

LAB 6 ELECTRICAL CIRCUITS
May 1, 2017
Lab 6 Set-up and Figure 1
1
LAB 6 ELECTRICAL CIRCUITS
May 1, 2017
OVERVIEW:
Electrical energy is useful when changed to heat, light, or mechanical energy. An electrical
circuit is required to convert electrical energy to a useful form. An electrical circuit has four
essential parts: a power source, a control element, conductors and a load. See figure A. The
power source supplies electrical energy to the circuit. The control element is a switch, a dimmer
or a variable speed control for the circuit. The conductor provides the path for the current flow
through the circuit. The load converts electrical energy to a useful form.
A series circuit contains only one conductive path for the current. See figure B. As the current
travels around the circuit, the voltage drops across each load when converting the electrical
energy to other energy forms. The total voltage across the circuit must equal the sum of the
voltages used up in each load. This can be expressed by the following equation:
𝐕𝐒𝐎𝐔𝐑𝐂𝐄 = V1 + V2 + V3
A parallel circuit contains two or more current paths. See figure C. The current in a parallel
circuit divides, and each path conducts only a portion of the total current. The sum of these
currents equals the total current leaving the battery or voltage source. In a parallel circuit, the
voltage across each load is the same as the voltage read directly across the battery or voltage
source.
𝑰𝑻𝒐𝒕𝒂𝒍 = 𝑰𝟏 + 𝑰𝟐 + 𝑰𝟑
𝐕𝐒𝐎𝐔𝐑𝐂𝐄 = 𝐕𝟏 = 𝐕𝟐 = 𝐕𝟑
In this experiment you will construct a series and a parallel circuit, using light bulbs as the load.
The voltage is measured "across the load", which means that the meter must be connected in
parallel with the load. This means that the voltmeter is
connected with the + probe on the side of the bulb closest to the
positive (+) terminal of the battery, and the (-) probe on the
other side of the bulb. Notice that the meter is measuring
potential difference (voltage), not current (amperage).
2
LAB 6 ELECTRICAL CIRCUITS
May 1, 2017
OBJECTIVES:
A) Construct a series and parallel circuit from a schematic diagram.
B) Draw a schematic diagram of a series and a parallel circuit.
C) Measure the voltage drops around a series and parallel circuit.
EQUIPMENT REQUIRED:
Circuit Panel
Universal Lead Set
Two Lamps on Mounted Base
Hook-Up-Wire & Strippers
Circuit Panel Easel
SPST Knife Switch
6V Battery
Digital Multi-meter (DMM)
Lab Equipment Discussion:
The Circuit Panel has 150 bronze conducting islands. Each island has five holes in it, into which
stripped wire or test leads with spring tips may be inserted. All wires plugged into the same
island are electrically connected. See Figure 5.
Many of the components needed for your experiments are mounted on boards that fit into your
Circuit Panel. To mount these components to the Circuit Panel, position the component so that
each mounting pin is inserted into a separate island. Figure 6 shows the correct placement of the
SPST (single-throw single-pole) Knife Switch on the Circuit Panel.
You use segments of hook-up wire to connect components together on your Circuit Panel. Cut
wire to the necessary length, and strip approximately 3/4" of insulation off of each end. This will
allow proper insertion into the island holes. See Figure 7.
3
LAB 6 ELECTRICAL CIRCUITS
May 1, 2017
PROCEDURE:
The basic setup for this experiment is shown in Figure 1.
A) VOLTAGE DISTRIBUTION IN A SERIES
CIRCUIT
1. Construct a two load series circuit, as pictured in Figure
8.
2. Close the knife switch. The bulbs should light. If they
do not, recheck your wiring and all connections.
3. You are going to measure the voltage across each lamp,
and the voltage of the power source. Figure 9 shows the
polarity of each load and the voltmeter connections for
measuring the voltage across lamp #1.
4. Set the voltmeter to measure DC voltage on the 20V
range. Touch the multimeter probes to the power supply leads where they connect to the
Circuit Panel. Be sure to observe the proper polarity. Read the voltage as displayed on the
multimeter, and record the value as the source voltage (V3) in Data Table 1.
5. Measure the voltage across each lamp in the circuit. Be sure to observe the proper polarity of
each load when connecting the multimeter probes. Record your measurements as V1 and V2 in
Data Table 1. Note the brightness of each lamp.
6. Draw a schematic diagram of your series circuit in the space provided. Indicate the polarity of
the battery with + and B) VOLTAGE DISTRIBUTION IN PARALLEL CIRCUITS
1. Construct a two load parallel circuit, using the schematic diagram of Figure 10.
2. Close the switch and check the circuit for proper operation.
3. Observe whether the bulbs appear to be brighter, dimmer, or the same brightness compared to
the series circuit of Part A. Complete this comparison by filling in the remarks between Tables
I and II,
4. Measure the voltage of the source (V𝑠 ), and the voltage of each lamp (V1 and V2 ).. Record the
readings in Data Table 2.
5. Draw a schematic diagram of your parallel circuit in the space provided. Indicate the polarity
of the battery.
6. Take the circuit apart. Turn the DMM off before storing.
ANALYSIS: Discuss the questions on the back of the lab form with your partners, filling in the
answers that you agree upon. If you cannot agree on a question, ask for help from the
instructor.
4
LAB 6 ELECTRICAL CIRCUITS
OBJECTIVES:
May 1, 2017
SKETCH OF LAB SET-UP:
DATA TABLE 1: SERIES CIRCUIT
Power Supply Voltage:
Vs =
Lamp #1 Voltage:
V1 =
Lamp #2 Voltage:
V2 =
SCHEMATIC DIAGRAM OF
SERIES CIRCUIT
LAMP BRIGHTNESS: OBSERVATIONS
DATA TABLE 2: PARALLEL CIRCUIT
Power Supply Voltage:
Vs =
Lamp #1 Voltage:
V1 =
Lamp #2 Voltage:
V2 =
SCHEMATIC DIAGRAM OF
PARALLEL CIRCUIT
5
LAB 6 ELECTRICAL CIRCUITS
May 1, 2017
Lab #6 ANALYSIS:
1. Using the voltage measurements from Data Table 1, verify that, for a series circuit that
Vs = V1 + V2.
2. Explain why the sum of the lamp voltages from question 1 might not equal the source voltage.
___________________________________________________________________________
3. Using the measurements from Table 2, verify that Vs = V1 = V2
4. In which circuit did the bulbs have the highest voltage?
______________________________________________________________________________
5. Explain why a difference in bulb brightness occurs for the two types of circuit.
______________________________________________________________________________
6. In the space below, draw a schematic diagram for a four load series circuit. Use lamps as the
loads, a battery for the source, and include an ON/OFF switch.
7. In the space below, show a schematic diagram a three load parallel circuit. Use two batteries
in series for the source and lamps as the loads. Include three switches in the circuit, each one
controlling a separate lamp.
6