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Craftsman Shielded Metal Arc Welding study materials
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Craftsman Shielded Metal Arc Welding practice questions

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Question 1Safety, Health and Environment for Arc Welding

A welder develops a gritty, burning sensation in both eyes several hours after arc welding without a helmet. Which agent from the arc is responsible for this condition?

  1. Ultraviolet radiation Correct answer.
  2. Infrared radiation
  3. Visible blue light
  4. Carbon monoxide gas

Explanation

The arc emits intense ultraviolet radiation that inflames the cornea and conjunctiva, producing photokeratitis (arc eye or welder's flash) after a delay of several hours. It can occur without looking directly at the arc because UV reflects off nearby surfaces.

Question 2Safety, Health and Environment for Arc Welding

What must be done before striking an arc on a steel drum that previously held a flammable solvent?

  1. Clean, purge and test the atmosphere first Correct answer.
  2. Weld at low amperage to reduce the risk
  3. Rinse it with water and weld at once
  4. Leave the bung open during welding

Explanation

An emptied drum still holds flammable vapour that can ignite or explode when heat is applied. The drum must be drained, cleaned, purged or inerted, and the atmosphere verified before any arc is struck.

Question 3Safety, Health and Environment for Arc Welding

Which eye protection is required when chipping slag from a completed weld?

  1. Safety glasses with side shields Correct answer.
  2. Tinted sunglasses
  3. No protection if the helmet is nearby
  4. Ordinary prescription glasses

Explanation

Chipping slag and grinding throw hard fragments toward the face at high speed, so impact-rated safety glasses with side shields are the minimum protection. A face shield may be worn over them for heavy chipping but does not replace the glasses.

Question 4Safety, Health and Environment for Arc Welding

Welding galvanized steel indoors produces a white fume. Which control should be applied first?

  1. Open a window for dilution
  2. Rotate welders to share exposure
  3. Wear a disposable dust mask
  4. Local exhaust at the arc Correct answer.

Explanation

Zinc oxide fume from galvanized coating causes metal fume fever, and capturing fume at the source with local exhaust is the most effective control. Respiratory protection is a backup where extraction cannot keep exposure below the limit.

Question 5Safety, Health and Environment for Arc Welding

Where should the work lead (ground clamp) be attached before SMAW welding?

  1. To a painted section of the workpiece
  2. To clean bare metal on the workpiece near the joint Correct answer.
  3. To a nearby steel building column
  4. To the gas cylinder rack

Explanation

The work lead must contact clean bare metal on the workpiece, close to the weld, so current returns through a low-resistance path. A poor or remote connection can overheat, arc, or energize structural steel, creating shock and fire hazards.

Question 6Safety, Health and Environment for Arc Welding

How must oxygen and acetylene cylinders be stored in a shop?

  1. Stacked together lying on their sides
  2. Locked inside a wooden storage cabinet
  3. Twenty feet apart or a 5-foot barrier Correct answer.
  4. Chained side by side in one corner

Explanation

Oxygen and fuel-gas cylinders must be kept at least 20 ft apart, or separated by a noncombustible barrier at least 5 ft high with a fire-resistance rating of at least half an hour. This prevents a fire on one cylinder from involving the other.

Question 7Safety, Health and Environment for Arc Welding

Before entering a confined space to weld, what is the correct order of atmospheric testing?

  1. Flammables, oxygen, toxics
  2. Oxygen, toxics, flammables
  3. Oxygen, flammables, toxics Correct answer.
  4. Toxics, flammables, oxygen

Explanation

Testing begins with oxygen because both a deficiency and an enrichment are immediately dangerous, and the oxygen level also changes how a flammable gas behaves. Flammable gas or vapour is checked next, and toxic contaminants last.

Question 8Safety, Health and Environment for Arc Welding

Welding stainless steel with SMAW can produce fume containing which substance that requires enhanced respiratory protection?

  1. Calcium carbonate
  2. Zinc oxide
  3. Iron oxide
  4. Hexavalent chromium Correct answer.

Explanation

Stainless steel contains chromium, and the arc converts some of it to hexavalent chromium, a carcinogen with a very low exposure limit. Welding on stainless therefore needs effective extraction and, where exposure remains, suitable respiratory protection.

Question 9Safety, Health and Environment for Arc Welding

A welder must make a short repair on a steel beam 30 ft from a stack of cardboard. What is the correct fire-prevention action?

  1. Proceed because the cardboard is beyond 25 ft
  2. Move the cardboard or guard it with a fire-resistant cover Correct answer.
  3. Post a fire watch only after welding is complete
  4. Wet the floor between the beam and the cardboard

Explanation

Hot-work rules require combustible material within 35 ft of the work to be moved or protected by fire-resistant guards or blankets. A fire watch must also be maintained during the work and for a set period after it ends.

Question 10Safety, Health and Environment for Arc Welding

A portable fume extractor with a flexible hood is used for SMAW. Where should the hood be positioned?

  1. Behind the welder at floor level
  2. Above the welder's head to catch rising fume
  3. Close to the arc, drawing fume away from the breathing zone Correct answer.
  4. Six feet from the arc to avoid spatter damage

Explanation

Fume capture depends on hood capture velocity, which falls sharply as distance increases, so the hood is placed as close to the arc as the work allows. It should draw fume away from the welder's face rather than across the breathing zone.

Question 11Safety, Health and Environment for Arc Welding

Which clothing practice is appropriate for a welder making a shielded metal arc welding pass?

  1. Wear a leather jacket or apron and trousers without cuffs over the boot tops Correct answer.
  2. Keep electrode stubs in open shirt pockets for quick access
  3. Wear a synthetic fleece jacket because it sheds spatter easily
  4. Roll trouser cuffs outward to catch stray spatter

Explanation

Leather clothing resists spatter and ultraviolet radiation better than ordinary work clothing. Trouser cuffs and open pockets can catch hot metal and cause burns. Synthetic fabrics can melt onto the skin when struck by spatter.

Question 12Safety, Health and Environment for Arc Welding

What is the minimum filter lens shade commonly specified for SMAW at about 100 A?

  1. Shade 13
  2. Shade 10 Correct answer.
  3. Shade 5
  4. Shade 14

Explanation

For shielded metal arc welding in the 60 A to 160 A range, a shade 10 lens is a common minimum. A lighter shade may not adequately reduce ultraviolet and visible radiation. Darker shades are generally reserved for higher-current welding.

Question 13Safety, Health and Environment for Arc Welding

Why must oxygen cylinder valves and fittings be kept free of oil and grease?

  1. Oxygen under pressure can ignite oil or grease violently Correct answer.
  2. Oil attracts moisture and causes valve corrosion
  3. Grease changes the oxygen purity and weakens the weld
  4. Oil can clog the regulator passages and reduce flow

Explanation

Oxygen-enriched systems greatly increase the flammability of oils and greases. A small amount of hydrocarbon contamination can ignite violently when exposed to pressurized oxygen. This is why oxygen fittings must be kept clean and oil-free.

Question 14Safety, Health and Environment for Arc Welding

In a typical hot-work program, what is the minimum time a fire watch should remain after SMAW has stopped in an area with combustible construction?

  1. 10 minutes
  2. 30 minutes Correct answer.
  3. 5 minutes
  4. 20 minutes

Explanation

Common hot-work programs require the fire watch to remain for at least 30 minutes after welding ends. Smoldering fires can develop slowly in concealed combustibles. The watch checks for smoke, heat, and other signs of fire before leaving.

Question 15Safety, Health and Environment for Arc Welding

A welder finds cracks in the insulating cover of the electrode holder. What is the correct action?

  1. Remove the holder from service and replace it Correct answer.
  2. Continue welding while wearing two pairs of gloves
  3. Wrap the cracks with electrical tape and continue welding
  4. Use the holder only at lower amperage

Explanation

Cracked insulation can expose energized metal and increase the risk of electric shock. The holder should be removed from service and replaced with an undamaged one. Field taping is not an acceptable repair for damaged welding holder insulation.

Question 16Safety, Health and Environment for Arc Welding

While a welder is working inside a permit-required confined space, who must remain at the entry point?

  1. A trained attendant with a means of summoning rescue Correct answer.
  2. Another welder who is waiting to take over
  3. The shop supervisor, if available
  4. No one, as long as the welder has a radio

Explanation

A trained attendant must stay outside the confined space to monitor the entrant and maintain communication. The attendant also summons rescue if conditions change or the welder needs help. A radio alone does not replace the attendant.

Question 17Safety, Health and Environment for Arc Welding

Which control best protects other workers from ultraviolet radiation and arc flash while SMAW is performed in a shared shop?

  1. Increasing general ventilation in the shop
  2. Turning off overhead lights near the welding area
  3. Asking nearby workers to wear sunglasses
  4. Placing opaque welding screens around the welding area Correct answer.

Explanation

Opaque welding screens block ultraviolet radiation and visible arc flash from reaching nearby workers. Ordinary sunglasses do not provide adequate protection against welding arc radiation. Ventilation addresses fume, not arc radiation.

Question 18Safety, Health and Environment for Arc Welding

Chronic overexposure to manganese in SMAW fume is associated with which health effect?

  1. Neurological effects resembling Parkinsonism Correct answer.
  2. Siderosis
  3. Metal fume fever
  4. Dermatitis

Explanation

Manganese affects the central nervous system and can cause neurological effects sometimes described as manganism. These effects can resemble Parkinsonism. Metal fume fever is more associated with zinc fume, while siderosis is associated with iron dust.

Question 19Safety, Health and Environment for Arc Welding

Why is the electrode holder a shock hazard even when no arc is being struck?

  1. It remains energized at open-circuit voltage whenever the welder is on Correct answer.
  2. It only becomes energized after the arc starts
  3. It stores high-pressure gas from the shielding coating
  4. It becomes radioactive after long use

Explanation

When the welding machine is on, the electrode holder is energized at open-circuit voltage even before an arc is established. Contact with the holder or electrode and a grounded surface can complete a circuit through the body. This is why dry insulation and dry gloves are essential.

Question 20Safety, Health and Environment for Arc Welding

SMAW must be done near an open floor drain in an area where flammable solvents are used. What should be done before welding?

  1. Place a fan at the drain to blow vapors into the shop
  2. Seal or cover the drain and confirm the atmosphere is not flammable Correct answer.
  3. Pour water into the drain to flush vapors away
  4. Proceed if no solvent odor is detected

Explanation

Floor drains can trap flammable vapors that may be released or ignited by welding sparks and heat. The drain should be sealed or covered and the atmosphere tested before hot work begins. Odor is not a reliable indicator of flammable vapor concentration.

Question 21Safety, Health and Environment for Arc Welding

A welder is kneeling on a damp concrete floor and changes electrodes without turning off the welding machine. Which condition most directly increases the likelihood of a serious secondary-voltage shock?

  1. The welding cable is routed across an insulated mat.
  2. The electrode coating is cracked and exposes the core rod.
  3. Wet contact with the floor lowers the body's electrical resistance. Correct answer.
  4. The machine's open-circuit voltage is lower than 50 V.

Explanation

Moisture on the skin and floor lowers resistance, so current from the electrode holder can pass through the body more readily. Dry insulation and lower open-circuit voltage reduce, rather than increase, shock risk. The condition that most directly raises the danger is the wet contact.

Question 22Safety, Health and Environment for Arc Welding

Which boot feature is most appropriate for a welder making shielded metal arc welds on a shop floor?

  1. Open laces that allow the boots to be removed quickly
  2. Leather uppers that resist spatter and hot slag Correct answer.
  3. Synthetic mesh uppers that let heat escape from the foot
  4. Rubber overshoes worn over cloth sneakers

Explanation

Leather uppers shed molten spatter and hot slag and provide a measure of thermal and electrical insulation. Synthetic mesh can melt or burn, open laces expose the foot, and rubber overshoes do not provide the needed resistance to hot metal.

Question 23Safety, Health and Environment for Arc Welding

A compressed gas cylinder must be moved across a shop on a hand truck. Which practice is correct?

  1. Lay the cylinder horizontally across the truck platform without restraint.
  2. Lift the cylinder by its valve protection cap.
  3. Secure the cylinder upright on the truck with the valve cap in place. Correct answer.
  4. Roll the cylinder on its bottom edge while holding the valve.

Explanation

A cylinder being moved should be secured against tipping, kept upright, and fitted with its valve protection cap until it is ready for use. Rolling or lifting by the valve can damage the valve and cause a sudden release of gas. An unrestrained horizontal cylinder can roll or fall.

Question 24Safety, Health and Environment for Arc Welding

A welding booth has only a roof-mounted general exhaust fan, with no local exhaust at the arc. What is the main limitation of this arrangement for controlling SMAW fume?

  1. It cannot remove particles and removes only gases.
  2. It removes fume only after the fume has passed through the welder's breathing zone. Correct answer.
  3. It requires a darker filter lens than local exhaust does.
  4. It overventilates the booth and makes the arc unstable.

Explanation

General exhaust dilutes and removes fume after it has risen through the area where the welder breathes. Local exhaust captures fume near the arc before it reaches the breathing zone, so it is more effective at the source. General exhaust is not inherently unable to remove particles, and it does not affect arc stability or lens shade.

Question 25Safety, Health and Environment for Arc Welding

A welding machine's control panel catches fire while the machine is still energized. Which extinguisher classification is appropriate for this electrical fire?

  1. Class D
  2. Class C Correct answer.
  3. Class B
  4. Class A

Explanation

Class C extinguishers are intended for fires involving energized electrical equipment. Once the equipment is de-energized, the burning material's class determines the extinguisher, but the immediate hazard is electrical. Class A, B, and D ratings address ordinary combustibles, flammable liquids, and combustible metals.

Question 26Safety, Health and Environment for Arc Welding

A steel bracket is coated with a paint that may contain lead. The welder must make a short SMAW repair. What is the correct preparation?

  1. Remove the coating from the weld zone and use appropriate respiratory protection. Correct answer.
  2. Burn the paint off with the arc before depositing the root pass.
  3. Apply a solvent wipe and weld while the surface is still wet.
  4. Weld through the paint quickly to limit fume generation.

Explanation

Coatings that may contain lead should be removed from the area that will be heated, and the welder should use respiratory protection appropriate to the exposure. Heating lead paint produces toxic fume and can contaminate the breathing zone. Welding through the coating or burning it off defeats fume control.

Question 27Safety, Health and Environment for Arc Welding

An engine-driven welder is parked outside a confined space with its exhaust outlet close to the space opening. Why is this arrangement hazardous?

  1. The engine's radio-frequency noise can interfere with the electrode holder.
  2. The engine's cooling air can overheat the confined space.
  3. The engine alternator can backfeed the confined-space lighting circuit.
  4. Carbon monoxide in the exhaust can enter the space and accumulate. Correct answer.

Explanation

Engine exhaust contains carbon monoxide, which is colorless and odorless and can be drawn into a confined space and accumulate to dangerous levels. The welder should be located so exhaust discharges away from openings and the space atmosphere should be monitored. Noise, cooling air, and lighting circuits are not the primary reason this placement is hazardous.

Question 28Safety, Health and Environment for Arc Welding

Why should hot slag and stub ends be placed in a metal container rather than a general trash can after SMAW?

  1. The trash can may be needed for paper waste.
  2. The slag will cool faster in a metal container.
  3. Hot slag can ignite combustible waste and start a fire. Correct answer.
  4. The metal container prevents the slag from becoming airborne.

Explanation

Slag and stub ends can remain hot long enough to ignite paper, wood, and other combustible waste in a general trash can. A metal container confines the hot material and reduces the chance of a smoldering fire. The container is used for fire prevention, not for airborne dust control or faster cooling.

Question 29Safety, Health and Environment for Arc Welding

A welder is issued a tight-fitting disposable particulate respirator for SMAW fume. Which requirement applies before the respirator is used?

  1. The filter must be replaced at the start of every shift.
  2. The welder must be fit-tested and perform a user seal check. Correct answer.
  3. The welder must use it only inside a confined space.
  4. The respirator must be shared with the helper to save cost.

Explanation

A tight-fitting respirator requires a medical evaluation, fit testing, and a user seal check before each use so that it can provide the expected protection. It is not limited to confined spaces, its filter is replaced when needed rather than necessarily every shift, and it must not be shared.

Question 30Safety, Health and Environment for Arc Welding

The disconnect for a stationary SMAW machine is in a locked electrical room controlled by another contractor. A welder must replace a damaged input cable. What is the correct procedure?

  1. Apply your own lock and tag to the disconnect after coordinating with the authorized person, then verify the machine is de-energized. Correct answer.
  2. Tape over the disconnect handle and post a handwritten note at the machine.
  3. Ask the other contractor to unlock the room and leave the disconnect closed while you work quickly.
  4. Turn the machine's power switch to off and begin work because the switch is the disconnect.

Explanation

Servicing input wiring requires lockout/tagout by an authorized person, with a personal lock and tag applied and the absence of voltage verified before work begins. Coordination is needed because the disconnect is controlled by another contractor. Taping a handle, posting a note, or relying on the machine switch does not provide lockout protection.

Question 31Welding Fundamentals, Power Sources and Equipment

A SMAW power source has a drooping (constant-current) volt-ampere characteristic. What does this mean for the welder?

  1. Welding current rises steeply whenever arc voltage rises
  2. Welding current is fixed by open-circuit voltage and cannot be adjusted
  3. Welding current drops to zero as soon as the arc is lengthened
  4. Welding current changes only slightly over a wide range of arc voltage Correct answer.

Explanation

A drooping curve falls steeply, so a large change in arc voltage produces only a small change in welding current. This lets the welder vary arc length to control the weld without current swinging widely, and it also limits current when the electrode shorts to the work.

Question 32Welding Fundamentals, Power Sources and Equipment

What is the name for the voltage present at a SMAW machine's output terminals before the arc is struck?

  1. Short-circuit voltage
  2. Open-circuit voltage Correct answer.
  3. Nominal input voltage
  4. Arc voltage

Explanation

Open-circuit voltage is the voltage across the output terminals when no arc is burning, and it is present whenever the machine is switched on. It is higher than arc voltage, roughly 50 to 90 volts versus 20 to 35 volts, and it is what helps establish the arc.

Question 33Welding Fundamentals, Power Sources and Equipment

The electrode holder is connected to the positive output terminal and the work clamp to the negative terminal. Which term describes this setup?

  1. AC polarity
  2. DCEP, also called reverse polarity Correct answer.
  3. DC variable polarity
  4. DCEN, also called straight polarity

Explanation

Electrode positive is direct current electrode positive (DCEP), also called reverse polarity, and it puts more heat into the work for deeper penetration. Electrode negative is DCEN, or straight polarity, which puts more heat into the electrode.

Question 34Welding Fundamentals, Power Sources and Equipment

A SMAW power source is rated 200 A at 60% duty cycle on a 10-minute basis. At 200 A, how is each 10-minute period divided?

  1. 4 minutes welding and 6 minutes cooling
  2. 10 minutes welding and no cooling
  3. 6 minutes welding and 4 minutes cooling Correct answer.
  4. 5 minutes welding and 5 minutes cooling

Explanation

Duty cycle is the percentage of a 10-minute period that a machine can operate at a given current. At 60% and 200 A, the machine can weld for 6 minutes and must cool for the remaining 4 minutes before the next cycle begins.

Question 35Welding Fundamentals, Power Sources and Equipment

A welder running at the machine's rated output on a hot day sees the arc stop and the thermal overload light come on. What is the correct response?

  1. Let the machine cool, then lower the current or duty cycle Correct answer.
  2. Switch off the cooling fan so the machine stops tripping
  3. Bypass the overload device so the job can be finished
  4. Raise the current setting and keep welding until the light clears

Explanation

The thermal overload device trips when the machine has exceeded its duty cycle or is overheated. The correct action is to let the fan cool the machine and then reduce the current or the arc-on time; bypassing the device or removing cooling will damage the machine.

Question 36Welding Fundamentals, Power Sources and Equipment

Why should welding cable size be increased when the leads must be made very long?

  1. To change the output from AC to DC
  2. To limit voltage drop and heating in the cable run Correct answer.
  3. To raise the open-circuit voltage at the stinger
  4. To increase the duty cycle rating of the power source

Explanation

Long leads add resistance, which causes voltage drop along the cable and heating of the conductor. Increasing cable size, which means a smaller AWG number, lowers resistance so the arc still receives enough current; keeping leads short and untangled also helps.

Question 37Welding Fundamentals, Power Sources and Equipment

Why does direct current generally give a steadier SMAW arc than alternating current?

  1. Current never crosses zero, so the arc stays steadier Correct answer.
  2. It removes the need for a constant-current characteristic
  3. It removes the need for a work clamp
  4. It allows the use of smaller electrode holders

Explanation

Alternating current passes through zero every half-cycle, so the arc briefly extinguishes and must restrike 100 or 120 times per second. Direct current flows continuously in one direction, giving a more stable arc, which is an advantage with certain electrodes, low currents, and out-of-position work.

Question 38Welding Fundamentals, Power Sources and Equipment

What is the main job of the transformer in a transformer-type SMAW power source?

  1. To store energy for the arc between cycles
  2. To step line voltage down to welding level and isolate the output Correct answer.
  3. To convert the AC output to DC for the arc
  4. To increase the open-circuit voltage above the input line voltage

Explanation

The main transformer steps the incoming line voltage down to the low voltage needed for welding and isolates the welding circuit from the input supply. Current is then controlled by the machine's reactance or tap settings; rectification, when present, is done by a separate bridge.

Question 39Welding Fundamentals, Power Sources and Equipment

Which condition most often causes arc blow during SMAW?

  1. Alternating current crossing zero many times each second
  2. Holding the arc shorter than the diameter of the electrode
  3. Magnetic deflection of a DC arc near the joint ends Correct answer.
  4. Moisture absorbed in the electrode coating

Explanation

Direct current sets up a magnetic field around the arc and the work. When that field is unbalanced, for example near the end of a joint, with the work clamp far away, or with cables coiled near the arc, the arc is deflected. AC tends to cancel these forces, so switching to AC, moving the clamp, or shortening the arc reduces arc blow.

Question 40Welding Fundamentals, Power Sources and Equipment

In a transformer-rectifier SMAW machine, what does the DC reactor in the output circuit do?

  1. It limits open-circuit voltage to a safe value
  2. It smooths the rectified current and stabilizes the arc Correct answer.
  3. It changes the machine from constant current to constant voltage
  4. It rectifies the AC from the transformer into DC

Explanation

After rectification the current is pulsating DC. The reactor, an inductor, opposes rapid current change, smoothing the output and helping the arc re-establish after each pulse, which gives a steadier arc and less spatter. It does not rectify the current or alter the machine's constant-current characteristic.

Question 41Welding Fundamentals, Power Sources and Equipment

In shielded metal arc welding, what is the primary purpose of the work clamp?

  1. It supplies shielding gas to the arc.
  2. It sets the welding current before the arc starts.
  3. It completes the welding circuit through the workpiece. Correct answer.
  4. It holds the electrode at the correct angle.

Explanation

The work clamp provides the return path for welding current from the workpiece back to the power source. A clean, tight connection keeps resistance low; a poor connection can overheat or cause an erratic arc.

Question 42Welding Fundamentals, Power Sources and Equipment

In a transformer-rectifier SMAW power source, what is the function of the rectifier?

  1. It limits the machine's duty cycle.
  2. It converts AC from the transformer to DC. Correct answer.
  3. It steps down the input voltage.
  4. It provides a high-frequency start pulse.

Explanation

The rectifier is a diode assembly that changes the transformer's AC output into DC. The reactor then smooths the rectified current for a steadier arc.

Question 43Welding Fundamentals, Power Sources and Equipment

What does the arc force (dig) control on a SMAW machine primarily change?

  1. It sets the open-circuit voltage.
  2. It increases current when the arc is shortened. Correct answer.
  3. It controls the shielding gas flow.
  4. It changes the output polarity.

Explanation

Arc force, sometimes called dig, temporarily raises current as the arc gets short. This helps prevent the electrode from sticking and maintains penetration when the welder pushes into the joint.

Question 44Welding Fundamentals, Power Sources and Equipment

Which welding polarity generally produces greater weld penetration in SMAW?

  1. Direct current with a pulsed arc
  2. Direct current, electrode positive Correct answer.
  3. Direct current, electrode negative
  4. Alternating current

Explanation

With direct current electrode positive (DCEP), more heat is concentrated at the workpiece, which generally gives deeper penetration. DCEN puts more heat into the electrode, so it is often used for thinner material.

Question 45Welding Fundamentals, Power Sources and Equipment

Why do SMAW power sources have a maximum open-circuit voltage limit, often around 80 volts?

  1. To increase the deposition rate
  2. To reduce the risk of electric shock to the welder Correct answer.
  3. To stabilize the AC arc
  4. To prevent arc blow

Explanation

Open-circuit voltage is present at the electrode holder before the arc is struck, when the welder may be in contact with the work. Standards limit OCV to reduce the severity of electric shock.

Question 46Welding Fundamentals, Power Sources and Equipment

How is welding current commonly adjusted on a basic transformer-type AC SMAW machine?

  1. By changing the transformer turns ratio or moving a coil Correct answer.
  2. By adjusting the shielding gas flow
  3. By changing the length of the welding cables
  4. By changing the electrode diameter

Explanation

In a transformer-type AC machine, current is set by changing the effective turns ratio or by moving a coil or magnetic shunt. These changes alter the leakage reactance and thus the output current.

Question 47Welding Fundamentals, Power Sources and Equipment

An engine-driven SMAW generator is running at low idle instead of weld speed. What is the likely effect on the welding output?

  1. The output polarity reverses.
  2. The welding output becomes low and unstable. Correct answer.
  3. The open-circuit voltage becomes zero.
  4. The duty cycle rating increases.

Explanation

An engine-driven generator must run at its designated weld speed to produce the rated voltage and current. At low idle, the output is reduced and the arc can be weak or unstable.

Question 48Welding Fundamentals, Power Sources and Equipment

On a drooping SMAW power source, what happens to welding current as the arc is lengthened from a normal arc length?

  1. The current decreases somewhat and the voltage rises. Correct answer.
  2. The current stays the same and the voltage stays the same.
  3. The voltage falls and the current rises sharply.
  4. The current increases and the voltage falls.

Explanation

A drooping characteristic has a steep volt-ampere curve. Lengthening the arc raises arc voltage and, along that curve, reduces welding current; too long an arc can cause instability and spatter.

Question 49Welding Fundamentals, Power Sources and Equipment

A SMAW machine rated for 230 V single-phase input is connected to a 208 V supply. What is the most likely result at the welding arc?

  1. The maximum welding output is reduced and the arc may be weak. Correct answer.
  2. The welding current rises above the rated value.
  3. The output polarity reverses.
  4. The duty cycle rating doubles.

Explanation

A machine designed for 230 V input has less primary voltage available on a 208 V supply. The secondary output is reduced, so maximum welding current and arc stability may suffer.

Question 50Welding Fundamentals, Power Sources and Equipment

A welder notices that the work clamp and its cable get very hot during welding while the electrode cable stays cool. What is the most likely cause?

  1. The open-circuit voltage is too high.
  2. The electrode is too large for the joint.
  3. The work clamp connection has high resistance. Correct answer.
  4. The welding cable is too short.

Explanation

Heat at the work clamp and its cable points to high resistance in that part of the circuit. A loose clamp, dirty work surface, or damaged cable connection can cause overheating and an erratic arc.