Karnataka SSLC Automobile - NSQF (KSEAB) flashcards

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

Compression ratio formula

Compression ratio equals swept volume plus clearance volume, divided by clearance volume. It states how far the charge is squeezed; petrol engines typically run 8:1 to 12:1 and diesels 16:1 to 22:1.

Vernier calliper least count

Least count is one main-scale division divided by the number of vernier divisions. A 1 mm main scale with 50 vernier divisions gives 0.02 mm resolution, so readings are taken to two decimal places.

Micrometer least count

Least count equals screw pitch divided by thimble divisions. A 0.5 mm pitch screw with a 50-division thimble resolves 0.01 mm, allowing precise measurement of shaft and valve stem diameters.

Torque wrench valid range

A torque wrench is accurate only in the middle of its scale, roughly 20 to 80 percent of full range. Return the setting to zero after use and calibrate annually to keep readings trustworthy.

Four-stroke cycle

The engine repeats intake, compression, power and exhaust in four piston strokes. The crankshaft turns twice per cycle while the camshaft turns once, giving one power stroke per cylinder per two revolutions.

Valve clearance effects

Too little clearance holds valves off their seats, causing leakage, compression loss and burnt valves. Too much clearance causes tapping noise, reduced lift and rapid cam and rocker wear.

Firing order 1-3-4-2

This common inline four-cylinder order balances crankshaft load and spaces power strokes evenly. Ignition leads and injection timing must follow it; swapping two leads creates misfire and rough running.

Clutch pedal free play

Free play is the pedal travel before the release bearing touches the pressure plate, usually 10 to 25 mm. Too little causes slip and bearing wear; too much causes drag and difficult gear engagement.

Torque converter stall speed

Stall speed is the maximum engine speed reached with the output shaft held stationary and full throttle applied. It tests converter and engine matching; low stall suggests a worn converter or restricted engine output.

Differential gear ratio

The ratio is ring gear teeth divided by pinion teeth. It multiplies gearbox output torque and reduces speed at the wheels; a higher numerical ratio improves pulling power but raises engine speed.

Ackermann steering geometry

Ackermann geometry turns the inner road wheel through a larger angle than the outer wheel. Both wheels then follow circles about a common centre, preventing tyre scrub and reducing wear during turns.

Wheel alignment angles

Caster, camber, toe and kingpin inclination define wheel position. Incorrect toe causes feathered tyre wear; wrong camber wears one edge; excessive caster raises steering effort but improves straight-line stability.

Pascal's law in brakes

Pressure applied to a confined fluid is transmitted equally in all directions. In hydraulic brakes a larger wheel-cylinder piston therefore produces greater clamping force than the small master-cylinder piston.

Brake fluid hygroscopy

DOT 4 brake fluid absorbs moisture from air, lowering its boiling point and risking vapour lock under heavy braking. It is replaced about every two years or when a tester shows moisture above roughly three percent.

Ohm's law and power

Voltage equals current times resistance, and power equals voltage times current. A 55 W headlamp on a 12 V supply therefore draws about 4.6 A, which sets the fuse and wire rating.

Lead-acid cell voltage

Each lead-acid cell produces about 2.1 V, so a six-cell battery gives 12.6 V at rest when fully charged. Charging voltage from the alternator is held near 13.8 to 14.4 V.

Series versus parallel circuits

In a series circuit the current is identical everywhere and voltages add. In a parallel circuit the voltage is common and currents add, which is why vehicle lamps are wired in parallel.

CAN bus lines

CAN bus uses two twisted wires, CAN-H and CAN-L, carrying differential signals at about 500 kbps. A short or open on either line can disable several electronic modules at once.

Stoichiometric air-fuel ratio

Petrol burns completely at about 14.7 parts air to one part fuel by mass; diesel is near 14.5 to 1. Richer mixtures give more power but raise carbon monoxide and hydrocarbon emissions.

SAE oil grade meaning

In a grade such as 15W-40, the number before W rates cold flow and the number after rates hot viscosity. The oil behaves like 15 grade when cold and 40 grade at operating temperature.

Radiator cap pressure rating

A cap rated about 0.9 to 1.1 bar raises coolant boiling point above 120 degrees Celsius with a glycol mix. A weak cap lets the system boil early and causes overheating under load.

Coolant mixture ratio

A 50:50 mix of ethylene glycol and water protects against freezing near minus 37 degrees Celsius and raises boiling point. Never open a pressurised cap while the engine is hot.

Tyre tread wear limit

The legal minimum tread depth is 1.6 mm, marked by wear indicator bars across the grooves. Tyres at the limit lose wet grip and are rejected during inspection.

Cold tyre pressure rule

Tyre pressure is set cold, before driving. Pressure rises about 0.3 bar when hot, so a hot tyre must never be bled down to the cold figure or it will be under-inflated.

PDI checklist purpose

Pre-delivery inspection confirms fluid levels, battery charge, tyre pressures, wheel nut torque, lamp and horn function and a road test before a new vehicle is handed to the customer.

Body filler thickness limit

Body filler is applied in thin coats over clean, abraded bare metal. Layers beyond about 3 mm tend to crack and shrink, so deeper damage is corrected by panel beating first.

Etch primer use

Etch primer contains acid that keys into bare aluminium and galvanised steel, giving corrosion protection and paint adhesion. It is applied thinly before epoxy primer or primer surfacer.

Orange peel paint defect

Orange peel is a bumpy surface like citrus skin, caused by too little thinner, low spray pressure or a fast pass. A run, by contrast, means too much material or too slow a pass.

Active listening technique

Active listening means facing the speaker, keeping eye contact, not interrupting, paraphrasing the message back and asking clarifying questions so misunderstanding is caught early.

Break-even quantity formula

Break-even quantity equals fixed cost divided by selling price per unit minus variable cost per unit. It states how many jobs must be sold before the workshop starts making profit.

Job card contents

A job card records customer complaint, authorised work, parts used, labour hours, technician name and customer signature on delivery. It protects both workshop and customer in disputes.

Cylinder head torque sequence

Cylinder head bolts are tightened from the centre outward in two or three stages to the specified torque, following the manufacturer's pattern. This spreads clamping load and prevents head distortion.