Lesson Plan
Course Title: Welding
Session Title: Welding Circuit
Performance Objective:
Upon completion of this assignment, the student will be able to understand
the basic welding circuit and its components.
Specific Objectives:
Define basic terminology
Label electrode negative and electrode positive diagrams
Illustrate an alternating current
Identify circuitry activity on a welding machine
Preparation
TEKS Correlations:
This lesson, as published, correlates to the following TEKS. Any changes/alterations
to the activities may result in the elimination of any or all of the TEKS listed.
Welding:
 130.323(c)(2)(F)
…demonstrate skills related to health and safety in the workplace, as specified by
appropriate government regulations.
 130.323(c)(4)(A)(B)(C)
…use welding equipment according to safety standards;
…properly dispose of environmentally hazardous materials used in welding; and
…use appropriate personal protective equipment as needed to follow safety
measures.
 130.323(c)(5)(A)(B)(C)(D)(E)(F)
…demonstrate knowledge of a welding blueprint;
…interpret blueprints, drawings, charts, and diagrams;
…analyze components of the welding symbol;
…analyze types of welding joints;
…analyze positions of welding; and
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…identify types of welds such as fillet, groove, spot, plug, and flanged.
Interdisciplinary Correlations:
English:
 110.42(6)(A) – Reading/word identification/vocabulary development
…expand vocabulary development through wide reading, listening, and
discussing;
Instructor/Trainer
References:
GTAW Student Material booklet Mid-America Vocational Curriculum Consortium (1984)
Modern Welding (2004)
Welding Principles and Applications (1999)
Instructional Aids:
1. Welding Machine Basics PowerPoint Presentation
2. DCEN Handout
3. DCEN Worksheet
4. DCEP Handout
5. DCEP Worksheet
6. AC Handout
7. AC Worksheet
8. Ohm’s Law Handout
9. Welding a Circuit Test
10. Welding a Circuit Test Key
Materials Needed:
Class copies of DCEN diagram
Class copies of DCEP diagram
Class copies of AC diagram
Equipment Needed:
Computer & monitor to support PowerPoint
Overhead projector
Learner
The student should provide writing instrument and paper for note-taking.
Introduction
Introduction (LSI Quadrant I):
A welding machine is powered by electricity. It is vital to have an understanding of how
electric current plays an integral role in the function of the welding machine and in the
process itself.
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Outline
Outline (LSI Quadrant II):
I. Terminology (students take notes; this will serve as a Guided Practice activity)
A. Electrons – flow through a conductor from negative (-) to positive (+)
B. Electricity – flow of electrons (produces heat)
C. Air gap – space between the electrode and the work item
D. Arc – produced by electrons jumping across the air gap (produces
great deal of heat)
E. Voltage (V) – measurement of electrical pressure (controls the
maximum gap the electrons can jump to form an arc) *like pounds per
square inch (psi), dealing with pressure (use the Ohm’s Law transparency)
F. Amperage (A) – measurement of total number of electrons flowing
(controls the size of the arc) *like gallons measures water
G. Wattage (W) – calculated by multiplying (V) x (A) is the measurement
of the amount of electrical energy or power in the arc; the amount of watts
being put into a weld per inch controls the width and depth of the weld
bead
H. Duty Cycle – the amount of time a welding machine can be used
continuously
II. Currents (use transparencies for AC, DCEN, DCEP; students should have
copies of the diagrams so they can label them; this will serve as a Guided
Practice activity)
A. AC (Alternating Current) – electrons change direction every 1/120 of a
second so that the electrode and work alternate thereby making a
balanced work load evenly distributed
B. DCEN (Direct Current Electrode Negative) – electrode is negative, work
is positive; produces high electrode melting rate
C. DCEP (Direct Current Electrode Positive) – electrode is positive, work
is negative; produces the best welding arc characteristics
III. Welding Machines
A. Instructor should show PowerPoint presentation (students take notes)
B. Complete Independent Practice activity over welding machine circuitry
IV. Review
V. Test
Application
Guided Practice (LSI Quadrant III):
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Taking notes over terminology and labeling diagrams over currents
Independent Practice (LSI Quadrant III):
During the Independent Practice activity, small groups of students are sent out into the
welding shop to look at the welding machines and gather information. Each group
should come back from their assigned welding machine with the following information:
1. Is the machine AC or AC/DC? 2. What voltage does it run on? 3. What is the Duty
Cycle of the machine? The groups should return with their information to be used in a
full group discussion over the various machines in the shop.
Summary
Review (LSI Quadrants I and IV):
Check for mastery/understanding by orally reviewing the students on the information.
Answer any questions the class may have. Ask individual students to contribute one fact
or principle he learned during the lesson. Make a list of these on the board or overhead.
Evaluation
Informal Assessment (LSI Quadrant III):
Instructor should monitor student understanding throughout the lesson. If further
explanation is needed on a given topic, instructor should elaborate or re-teach that
portion of the lesson.
Formal Assessment (LSI Quadrant III, IV):
Mastery of at least 70% of objective test.
Extension/Enrichment (LSI Quadrant IV):
For those students who need remediation, a re-teach and review session will reinforce
the topics of concern. The remediation will need to be tailored to the individual needs of
the student.
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ALTERNATING CURRENT (AC) HANDOUT
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ALTERNATING CURRENT (AC) WORKSHEET
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OHM’S LAW HANDOUT
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DCEN HANDOUT
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DCEN WORKSHEET
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DCEP HANDOUT
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DCEP WORKSHEET
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Welding Circuit Test
Name: ______________________
1. Describe Voltage (V)
2. Describe Amperage (A)
3. Describe Wattage (W)
4. Explain the process of an AC (Alternating Current)
5. What is meant by a machine’s Duty Cycle?
6. How much heat does the positive side get?
7. What are the common voltages welders run on?
8. Describe the difference between straight polarity and reverse polarity.
9. If you have 30 volts and 110 amps, what is your wattage?
10. What produces an arc in a welding current?
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Welding Circuit Test KEY
1. Describe Voltage (V)
Measurement of electrical pressure (just like psi is used for water pressure)
2. Describe Amperage (A)
Measurement of total number of electrons flowing (same way gallons measures water
flowing)
3. Describe Wattage (W)
Measurement of amount of electrical energy
4. Explain the process of an AC (Alternating Current)
Electrons change direction every 1/120th of a second so that the electrode and work
alternate. The rapid reversal of current causes the welding heat to be evenly distributed
between the work and the electrode. The 50/50 distribution of heat gives the bead a
balance between penetration and build-up.
5. What is meant by a machine’s Duty Cycle?
The percentage of time a machine can run continuously.
(Example: 60% means 6 minutes running out of 10 minutes, with 4 minutes of rest time)
6. How much heat does the positive side get?
- 75%
7. What are the common voltages welders run on?
110, 220, 440
8. Describe the difference between straight polarity and reverse polarity.
Straight polarity, the stinger is negative.
Reverse polarity, the stinger is positive.
9. If you have 30 volts and 110 amps, what is your wattage?
330 watts
10. What produces an arc in a welding current?
The electrons jumping the resistance of the air gap
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