[01편]2025~2026년 농기계정비기능사 자격증 필기시험 기출 및 예상문제

Main ideas / lessons from the subtitles

This video reviews Agricultural Machinery Maintenance Technician exam questions (mostly multiple-choice). It emphasizes correct technical concepts and safety/maintenance procedures across:

• Engines (and clearances/wear)
• Power transmission
• Electrical systems
• Hydraulics
• Lubrication
• Fuel/ignition systems
• Workplace hazards and PPE

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Detailed breakdown of the question themes + key correct concepts

1) Engine & mechanical clearances / wear

Piston clearance (correct explanation)

• If piston clearance is small, friction heat increases due to contact with the cylinder wall → wear is likely.

Average piston speed calculation

• Given:
  • Piston stroke = 160 mm
  • Engine speed = 1600 rpm
• Result (as described): 8.53 m/s
• Method uses proportionality to rotational speed and the factor 2/60.

Compression ratio (gasoline example)

• Given:
  • Total displacement: 1000 cc
  • Combustion chamber volume: 200 cc
• Formula: (\text{Compression ratio} = 1 + \frac{V_d}{V_c})
• Result: 6:1

If engine compression test pressure is higher than specified

• Maintenance method mentioned: remove carbon deposits from the combustion chamber.

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2) Diesel ignition / knock / combustion-related properties

“Ignition catalyst” not included

• Not an ignition catalyst: glycerin.

Diesel knock suppression

• Property related to reducing knock: cetane value/number
  • (Contrast: octane is for gasoline knock.)

If diesel output drops

• One stated cause: piston rings are seized.

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3) Fuel injection timing / adjustment (single-cylinder diesel)

When injection timing is delayed

• Adjustment method given:
  • Remove one 0.2 mm copper plate from the injection pump installation part.
• Subtitle also describes the effect:
  • Changing shim thickness by ~0.1 mm shifts timing by about ~1° faster (as described).

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4) Electrical / ignition system concepts

Headlight elements

• Bulb, reflector, lens

Lead-acid battery discharge reaction

• The subtitle indicates the correct answer choice: 1.

Electromotive force opposing change

• Defined as electromagnetic induction.

Starter motor not working (not a reason)

• Not a reason: fuel in the carburetor is full
• Other broad reasons listed include:
  • Loose terminals, broken/interrupted circuit, overload
  • Poor contact, battery discharge
  • Faulty switch
  • Pinion–ring gear meshing issues
  • Bearing issues

Function of throttle valve (gasoline carburetor)

• Regulates the amount of the mixture entering the engine.

Capacitor function (not correct statement)

• Not correct: “capacitor shortens interruption time to lower secondary voltage.”
• The subtitle’s correction indicates the direction should increase secondary voltage by shortening interruption time.

Fleming’s left-hand rule

• The middle finger points in the direction of current (mapping uses the subtitle’s numbering).

When spark doesn’t occur from a standard spark plug

• Not required/incorrect (per subtitle answer): internal cylinder compression pressure.

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5) Rotating equipment / PTO & rotary tiller / traction

Rotary tiller function/structure (incorrect statement)

• Incorrect: power transmission from PTO to tiller shaft changed from side drive to direct drive.

Automatic locking device on tractor

• Most suitable farmland: soil with weak propulsion force (subtitle references a “numerical value”).

Track width adjustment (power tiller)

• Not a method: “replace the steering clutch spring” (chosen as incorrect by the subtitle).

Turbine pump (centrifugal type) purpose

• Uses guide vanes to convert kinetic energy into pressure energy.

Disc plow / implement characteristic

• Not a characteristic: high power consumption
  • Subtitle claims disc plows have low power consumption.

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6) Hydraulic / lubrication / braking

Hydraulic system: cause of low hydraulic pressure (NOT a cause)

• Not a cause: “part of the URP is blocked” (as stated in the subtitle).
• Suction port pump blockage is mentioned as a relevant issue.

Power tiller transmission driven without lubrication (NOT a failure)

• Not a failure: transmission rotational force increases
• Likely harms listed include:
  • Overheating
  • Difficult driving
  • Loud noise

Poor braking despite pressing brake pedal (NOT a cause)

• Not a cause: hydraulic brake wheel cylinder hydraulic pressure is strong.

Clutch slipping while tractor climbs a hill (incorrect cause)

• Incorrect: excessive play in the clutch pedal
• Other causes given:
  • Oil on clutch plate
  • Severe wear
  • Low spring tension
  • Worn/deteriorated facing
  • Poor friction surfaces

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7) Safety management & PPE & hazard prevention

Grinder assembly safety when breakage risk exists

• Install a covering device to prevent fragments flying out.

Dust mask unsuitable condition

• Not suitable: mask with narrow field of view.

Grinder operating precautions (incorrect)

• Incorrect: using the grinder side to obtain a machined surface
  • Side use is only allowed if the wheel is designed for side grinding.

Power sprayer safety precaution (incorrect)

• Incorrect: “always work with your hands facing the wind when separating pesticides”
• Correct principle during spraying (per subtitle): work with your back to the wind.

AC welding electric shock prevention (NOT a method)

• Not correct (per subtitle): “use primary side movement and a low-voltage welder”
• Measures listed as acceptable include:
  • Automatic shock prevention device
  • Insulated rod holder
  • Correct/appropriate cables and electrical connections (including secondary common/appropriate line)
  • Insulated gloves
  • Proper connector gripping terminal
  • Grounding

Lifting heavy objects (incorrect technique)

• Incorrect: straighten legs, bend waist, and lift forcefully (“forced lifting”)
• Preferred approach:
  • Keep head/waist steady
  • Bend knees
  • Lift, then stand up slowly

Hand tools precaution

• Correct: “always drive a wedge into hammer material when using them” (as marked correct)
• Additional notes mentioned:
  • Be cautious about accidents during certain precision work
  • Don’t remove chips bare—use a brush/handle
  • Gloves/hammer context appears in the subtitle

Occupational disease caused by dust (NOT an occupational disease)

• Not listed as dust-induced: hearing loss.

Fuel storage safe handling (correct statement)

• Buy the appropriate amount and use most/all.
• Store remaining fuel separately in a fire-safe location.

Combine harvester storage/maintenance (NOT correct precaution)

• Not correct: “disassemble the feeder and store it separately”
• Correct long-term storage approach (per subtitle):
  • Run idle long enough to remove residue
  • Clean thoroughly
  • Store in a dry, ventilated place

Electric shock at AC welding / safety organization type

• Safety management organization where all workers participate and instructions spread quickly: direct staff organization

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8) Inspections & maintenance checklists

Tractor glazing system: NOT a 5-day inspection item

• Not: if the hydraulic system’s “5th” is insufficient, mix engine oil and gear oil and inject it
• Correct: refill with the same type of oil currently used.

Spark plug tests (not a test method)

• Not: intermittent test
• Other mentioned test methods include: Kimil test, spark test, insulation test.

Soup dryer burner inspection (incorrect item)

• Incorrect: electrode gap 5–10 mm
• Correct guidance (per subtitle):
  • Electrode gap 3 mm normal
  • Other checks include blower blades, nozzle spray condition, indicator lamp status.

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9) Electrical systems / battery wiring / protection

Connecting four OVT batteries when 20V is required

• Answer: series connection
• Reason:
  • Series increases voltage
  • Parallel increases capacity

Device to cut generator backflow when battery voltage is high

• Answer: cut-out relay

Starter/overcurrent phenomenon on a label

• Overcurrent occurs → connection breaks.

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10) Physics / electrical calculations & principles

Equivalent resistance

• Subtitle indicates the equivalent resistance is computed to 15 ohms (via (c + 1/10 + 1/10)).

Transformer turns/voltage ratio example

• Primary turns: 80
• Secondary turns: 320
• Secondary voltage: 80 V
• Primary voltage (as described): 20 V

Illuminance vs luminous intensity

• Example includes:
  • At 2 m distance, lux result given as 15
• Subtitle notes the idea:
  • Illuminance is proportional to luminous intensity divided by distance squared.

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11) Other topics: pest/chemical devices and drying systems

Pesticide powder sprayer device

• Subtitle references a term like “Sewege device” (likely misrecognized), described as a type of sprayer/powder application mechanism.

Storage-type dry dryer

• Dryer ventilates a small amount of air from beneath a perforated metal plate to prevent spoilage.

Grain drying system description

• Classified as a storage-type dry dryer.

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Methodology / instruction-style items explicitly mentioned

• Grinder assembly fragments

  • If breakage risk exists: install a covering device.

• Remove carbon build-up after abnormal compression test

  • If compression is higher than specified: remove carbon from the combustion chamber.

• Adjust single-cylinder diesel injection timing (delayed timing)

  • Procedure: remove one 0.2 mm copper plate.

• Refill tractor glazing/“5th” fluid correctly

  • If hydraulic “5th” is insufficient: refill with the same type of oil already in use.

• Dust mask suitability

  • Avoid masks with a narrow field of view.

• Power sprayer pesticide handling

  • During spraying: work with your back to the wind.

• AC welding electric shock prevention (correct measures)

  • Use an automatic electric shock prevention device
  • Use an insulated welding rod holder
  • Use correct cables and connections, including grounding
  • Wear insulated gloves
  • Use the correct connector gripping terminal

• Safe lifting heavy objects

  • Avoid: forced lifting by bending the waist and lifting aggressively
  • Prefer: head/waist steady → bend knees → lift → stand up slowly

• Fuel storage best practice

  • Buy/use appropriate amount; store remaining separately in a fire-safe place.

• Combine harvester long-term storage

  • Run idle to clear residue
  • Clean and lubricate sufficiently
  • Store in dry, ventilated conditions

• Spark plug test concepts

  • Recognize test methods include: Kimil test, spark test, insulation test
  • Not “intermittent test” (per subtitle)

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Speakers / sources featured

• No specific named speakers or external sources are identified.
• The “speaker” appears to be the video narrator/exam reviewer only, with occasional confusing/misaligned lines, but no identifiable credited person is provided.