Auto Information Practice Test 1: Drivetrain First

Answer: B

Correct answer: Leave them alone for trained technicians. Hybrid and electric vehicles carry high-voltage batteries and cables, usually with orange insulation, that can deliver a lethal shock. Basic diagnosis covers conventional 12 V systems only, so orange cables and high-voltage parts are left to trained technicians.

• A: Handling high-voltage cables can cause a lethal shock; they are not for home checks.
• B (correct): Orange insulation marks high-voltage parts, which should be handled only by trained technicians using the manufacturer's procedures.
• C: A 12 V test light is not rated for high-voltage systems and puts the user at risk.
• D: Disconnecting high-voltage cables is dangerous and requires special procedures and protective equipment.

Answer: D

Correct answer: Radiation. Radiation is heat carried by electromagnetic waves, mainly infrared, and it needs no contact or moving fluid. Very hot parts such as exhaust manifolds radiate strongly, which is why heat shields protect nearby wiring and fuel lines.

• A: Rising warm air does move some heat, but heat reaching your face sideways without moving air is mainly infrared radiation.
• B: Conduction needs direct contact or a material path, and you are not touching the manifold.
• C: Forced convection needs a pump or fan driving a fluid, and no air is blowing toward you.
• D (correct): Hot parts give off infrared waves that need no material in between, which is why heat shields are used near exhaust parts.

Answer: D

Correct answer: 0.004 Ω. Rearrange Ohm's law:

Even this tiny resistance wastes 0.6 V that the starter never receives, which is why ground straps matter.

• A: This multiplies voltage by current, which gives power in watts, not resistance.
• B: This divides current by voltage, which is the inverse of Ohm's law for resistance.
• C: The method is right but a decimal place slipped; 0.6 / 150 is 0.004.
• D (correct): R = V / I = 0.6 / 150 = 0.004 ohm.

Answer: A

Correct answer: 7.6:1. Low range is a separate reduction in the transfer case that multiplies whatever the transmission is doing. Combined reduction =

1, before the final drive is applied.

• A (correct): Ratios in series multiply: 3.8 × 2.0 = 7.6.
• B: This adds the ratios, but each stage scales the speed left by the one before it.
• C: This divides the ratios instead of multiplying them.
• D: This ignores the low range, which adds its own reduction on top of first gear.

Answer: D

Correct answer: Underinflation. Read the pattern: both outer edges worn suggests underinflation, center wear suggests overinflation, one shoulder suggests camber, and feathered edges suggest toe. Treat it as a clue and confirm by checking the pressure against the vehicle placard.

• A: Overinflation tends to wear the center of the tread, not both edges.
• B: A camber problem usually wears one shoulder, not both edges evenly.
• C: Imbalance is more often linked to cupped scallops and a speed-band shake.
• D (correct): An underinflated tire flexes and rides on its edges, wearing both shoulders.

Answer: C

Correct answer: 36 kW. Power is torque times angular speed:

Divide by 1,000 to convert: 36,000 W = 36 kW.

• A: This misplaces the decimal when converting 36,000 W to kilowatts.
• B: This divides torque by angular speed instead of multiplying them.
• C (correct): P = Tω = 240 × 150 = 36,000 W, which is 36 kW.
• D: This shifts the decimal the other way; 36,000 W is 36 kW, not 360 kW.

Answer: A

Correct answer: 140 N·m. Torque equals force times the perpendicular distance from the center.

• A (correct): Torque is force times lever arm: 400 x 0.35 = 140 N$\cdot$m.
• B: This divides the force by the lever arm instead of multiplying.
• C: This treats 35 cm as 0.035 m, a decimal slip in converting to meters.
• D: This ignores the lever arm; torque depends on the distance from the center as well as the force.

Answer: C

Correct answer: To cool the compressed air so it becomes denser. Compressing intake air raises its temperature, which makes it less dense. The intercooler removes that heat, so each cylinder receives more air mass, allowing more fuel and power while reducing the chance of knock.

• A: The turbo's compressor does the compressing; the intercooler is a heat exchanger, not a compressor.
• B: The intercooler sits in the air path, not the fuel path, and the boost system works on air.
• C (correct): Compressing air heats it; cooling it packs more air mass into each cylinder and lowers knock risk.
• D: Dust is removed by the air filter, which comes before the turbocharger.

Answer: C

Correct answer: About 4.0 L. Convert to centimeters (9.6 cm bore, 9.2 cm stroke), find one cylinder's volume, then multiply by 6.

• A: This is the volume of one cylinder only; it still has to be multiplied by six cylinders.
• B: This uses pi times the bore squared, treating the diameter as if it were the radius, which makes the answer four times too large.
• C (correct): Each cylinder sweeps about 666 cc, and six cylinders give about 3996 cc, or 4.0 L.
• D: This forgets to square the bore, multiplying 9.6 cm by 9.2 cm once instead of using 9.6 squared.

Answer: C

Correct answer: Seized rear self-adjusters, leaving a growing gap between shoes and drums. When drum lining wears, the gap between shoes and drum grows, so the wheel cylinder needs more fluid and more pedal travel to reach the drum. A self-adjuster normally takes up that gap; if it seizes, the pedal gets low and the parking brake, which uses the same rear shoes, needs more lever travel. A firm pedal and no leaks rule out air and fluid loss.

• A: Air would compress and make the pedal spongy, but this pedal is firm, and air would not affect the cable-worked parking brake.
• B: Lost booster assist makes the pedal hard to push; it does not make the pedal low or the parking lever travel farther.
• C (correct): As the lining wears and the adjuster no longer takes up the gap, the shoes travel farther, lowering the pedal and lengthening parking lever travel.
• D: Front pad wear may cause a squeal but would not change parking lever travel, and disc calipers adjust for wear on their own.