Maharashtra SSC Automotive Service Technician Pre-Voc/NSQF flashcards

41 cards. Read the term and the definition here. The deck at the top of this page is optional.

Fire class B

Fire involving flammable liquids such as petrol, diesel or paint thinner. Water spreads the burning liquid, so foam, dry powder or CO2 extinguishers are used instead.

Torque formula

Torque equals force multiplied by perpendicular distance from the pivot. A force of 100 newtons at 0.4 metres gives 40 newton-metres, which is the basis of torque wrench settings.

Vernier caliper least count

The smallest value a vernier caliper can read, found by dividing one main scale division by the number of vernier divisions. A 1 mm main division with fifty vernier divisions gives 0.02 mm.

Compression ratio

Swept volume plus clearance volume divided by clearance volume. It states how far the charge is compressed before ignition and influences power, efficiency and required fuel octane rating.

Clutch pedal free play

The small pedal movement, typically ten to twenty-five millimetres, before the release bearing touches the pressure plate. Without it the bearing wears and the clutch can slip.

Caster angle

The tilt of the steering axis from vertical when viewed from the side. Positive caster improves straight-line stability and self-centring of the steering after a turn.

Ohm's law

Voltage equals current multiplied by resistance in a circuit. It lets a technician calculate expected resistance or current from measured voltage, and power equals voltage times current.

Stoichiometric air-fuel ratio

The mass ratio of air to petrol that burns completely, about 14.7 to 1. Richer mixtures raise carbon monoxide and hydrocarbons, leaner mixtures raise oxides of nitrogen.

MIG welding

Metal inert gas welding uses a continuously fed consumable wire electrode and shielding gas to protect the molten pool. It suits thin steel body panels and gives high deposition rates.

OBD-II code families

Standardised diagnostic trouble codes are grouped by letter: P for powertrain, B for body, C for chassis and U for network communication faults between electronic control units.

Feedback in communication

The receiver's response confirming the message was understood. In a workshop, repeating a repair instruction back to the supervisor is a practical form of feedback.

Break-even quantity

Fixed cost divided by the difference between selling price per unit and variable cost per unit. It is the number of jobs needed before the workshop starts making profit.

Hydrogen charging hazard

Lead-acid batteries release hydrogen gas while charging. The area must be ventilated and free of sparks, flames and smoking, because hydrogen ignites at very low concentration.

Feeler gauge use

A set of thin steel blades of known thickness used to measure small gaps such as valve clearance. The correct blade gives a light drag when pulled through the gap.

Micrometer zero error

The reading shown when the anvils are closed. A positive or negative offset is added or subtracted from every measurement, so the instrument is checked before use.

Torque-to-yield bolt

A head or main bearing bolt tightened to a low torque then rotated through a specified angle. It stretches permanently and must be replaced, not reused, on reassembly.

Differential final drive ratio

The number of ring gear teeth divided by the number of pinion teeth. It multiplies gearbox output torque and determines engine speed for a given road speed.

Brake fluid hygroscopic property

Brake fluid absorbs moisture from the air over time. Absorbed water lowers the boiling point, causing vapour lock, a spongy pedal and reduced braking when hot.

Voltage drop test

Measuring voltage lost across a cable or connection while current flows. More than about half a volt indicates excessive resistance such as corrosion or a loose terminal.

EGR valve function

Exhaust gas recirculation returns a small amount of exhaust to the intake. This lowers peak combustion temperature and reduces oxides of nitrogen formation at part load.

Spray gun distance

The recommended gap between spray gun nozzle and panel, usually fifteen to twenty centimetres. Too close causes runs, too far causes dry overspray and rough orange-peel finish.

Freeze-frame data

A snapshot of sensor values and operating conditions stored by the control unit when a fault is set. It helps reproduce the conditions that triggered the code.

Job card purpose

A workshop document recording the customer complaint, vehicle details, work authorised, parts used, labour and technician signature, providing a traceable service record.

Quotation components

A written price estimate that separates parts cost, labour charge, taxes and validity period. It is approved by the customer before work begins to avoid billing disputes.

Jack stand rule

A hydraulic jack only lifts. The raised vehicle must rest on stands rated above the load, placed on level firm ground under the specified lifting points.

Dial indicator runout check

The gauge plunger is set perpendicular to a rotating surface. Total needle movement during one revolution gives runout, used for brake discs, shafts and gears.

Bore taper and ovality

Differences in cylinder diameter measured at several heights and in two directions. Exceeding the maker's limit requires reboring or a new liner and matching oversize piston.

Valve clearance too tight

Insufficient gap prevents the valve from seating fully. Hot gases escape past the valve face, causing burnt valves, compression loss and possible misfire.

Synchroniser function

A cone clutch inside a manual gearbox that brings the gear and shaft speeds together before engagement, preventing grinding when the driver shifts.

Camber angle

The inward or outward tilt of the wheel from vertical viewed from the front. Excessive camber causes uneven tyre wear on one shoulder and affects straight-line grip.

Alternator charging voltage

With the engine running and loads switched on, charging voltage is typically about 13.5 to 14.5 volts. Higher or lower readings indicate regulator or diode faults.

Three-way catalytic converter

An exhaust device that converts carbon monoxide, hydrocarbons and oxides of nitrogen into less harmful gases. It works efficiently only near the stoichiometric air-fuel ratio.

Welding helmet shade

The darkness rating of the filter lens. Higher shade numbers suit higher currents; arc welding of steel body panels typically uses shades ten to thirteen.

No-start diagnostic order

Check battery voltage, cranking speed, fuel pressure, ignition spark and compression in that order. This separates electrical, fuel and mechanical causes before parts are replaced.

Technical vocabulary precision

Terms such as clearance, tolerance, backlash and runout describe different conditions. Using them accurately in job cards and handovers prevents wrong repairs and miscommunication.

Customer complaint handling

Listen without interruption, apologise for the inconvenience, confirm the facts, offer a specific remedy with a time frame, then follow up after the vehicle is delivered.

PCV valve role

The positive crankcase ventilation valve meters blow-by gases from the crankcase back into the intake. A blocked valve raises crankcase pressure and causes oil seal leaks.

Wheel alignment toe setting

The difference between the front and rear distances across a pair of wheels. Incorrect toe causes rapid tyre scrub and is corrected by adjusting the tie rod ends.

Series versus parallel circuits

Series circuits share one current and divide voltage; parallel circuits share voltage and divide current. Vehicle lamps and accessories are wired in parallel so each works independently.

Waste oil disposal rule

Used engine oil, filters and coolant are hazardous waste. They are stored in labelled closed containers and handed to authorised recyclers with disposal records kept.

GST invoice essentials

A tax invoice shows supplier GSTIN, unique invoice number, date, description of parts and labour, taxable value, tax rate and amount, and the customer details.