1.
A 470 resistor and a 0.2 F capacitor are in parallel across a 2.5 kHz ac source. The admittance, Y, in rectangular form, is
Correct Answer
B. 2.12 mS + j3.14 mS
Explanation
The admittance of a parallel combination of a resistor and a capacitor can be calculated using the formula Y = G + jB, where G is the conductance and B is the susceptance. The conductance G is equal to the reciprocal of the resistance, and the susceptance B is equal to the reciprocal of the reactance of the capacitor, which is given by 1/(2πfC), where f is the frequency and C is the capacitance. In this case, the resistance is 470Ω and the capacitance is 0.2F. Plugging these values into the formulas, we get G = 1/470 and B = 1/(2π(2500)(0.2)). Simplifying these values, we get G = 2.12mS and B = 3.14mS. Therefore, the admittance is 2.12mS + j3.14mS.
2.
A positive angle of 30° is equivalent to a negative angle of
Correct Answer
B. –330°
Explanation
A positive angle of 30° is equivalent to a negative angle of -330°. This is because a positive angle of 30° represents a counterclockwise rotation of 30°, while a negative angle of -330° represents a clockwise rotation of 330° in the opposite direction. Since 330° is greater than 180°, it is considered a negative angle. Therefore, -330° is the correct answer.
3.
In a series RC circuit, 12 V_{(rms)} is measured across the resistor and 15 V_{(rms)} is measured across the capacitor. The rms source voltage is
Correct Answer
C. 19.2 V
Explanation
In a series RC circuit, the total voltage across the circuit is equal to the sum of the voltage across the resistor and the voltage across the capacitor. In this case, the voltage across the resistor is 12 V(rms) and the voltage across the capacitor is 15 V(rms). Therefore, the total voltage across the circuit, which is the rms source voltage, is 12 V(rms) + 15 V(rms) = 27 V.
4.
Solve the following equation for the two roots of x: x^{2} — 16 = 0
Correct Answer
C. X = 4, –4
Explanation
The given equation is a quadratic equation in the form of x^2 - 16 = 0. To solve this equation, we can factor it as (x - 4)(x + 4) = 0. Setting each factor to zero, we get x - 4 = 0 and x + 4 = 0. Solving these equations, we find that x = 4 and x = -4 are the two roots of the equation. Therefore, the correct answer is x = 4, -4.
5.
Solve the following equation for x, y, and z:
x – y + z = –1 –x + y + z = –1 x + 2y – 2z = 5
Correct Answer
A. X = 1, y = 1, z = –1
Explanation
The correct answer is x = 1, y = 1, z = -1. This is the solution to the system of equations given. By solving the system using elimination or substitution method, we can find the values of x, y, and z that satisfy all three equations. In this case, substituting the value of z = -1 into the first two equations allows us to solve for x and y, resulting in x = 1 and y = 1. Therefore, the correct answer is x = 1, y = 1, z = -1.
6.
At room temperature the current in an intrinsic semiconductor is due to
Correct Answer
D. Holes and electrons
Explanation
At room temperature, the current in an intrinsic semiconductor is due to both holes and electrons. In an intrinsic semiconductor, the number of free electrons and holes is equal. At room temperature, some electrons gain enough energy to break free from their covalent bonds and become free electrons, while leaving behind holes. These free electrons and holes are responsible for the flow of current in the semiconductor. Therefore, the correct answer is "holes and electrons."
7.
Work function is the maximum energy required by the fastest electron at 0 K to escape from the metal surface.
Correct Answer
B. False
Explanation
The explanation for the given correct answer is that the work function is not the maximum energy required by the fastest electron at 0 K to escape from the metal surface. The work function is actually the minimum energy required for an electron to be ejected from the surface of a metal, not the maximum energy. The maximum energy required by the fastest electron to escape from the metal surface is known as the stopping potential.
8.
If the valve clearances are excessively large, the problem that can arise is
Correct Answer
B. Incomplete valve closure
Explanation
If the valve clearances are excessively large, it means that there is too much space between the valve and the valve seat when the valve is closed. This can result in incomplete valve closure, meaning that the valve does not fully seal against the valve seat. This can lead to a variety of issues, such as loss of compression, poor engine performance, and potentially even engine damage.
9.
The brake pedal during ABS operation
Correct Answer
C. Transmits slight kickback to the driver's foot
Explanation
During ABS (Anti-lock Braking System) operation, the brake pedal is pushed upward forcefully, causing the pedal stroke to become longer. This forceful upward movement of the pedal can result in a slight kickback sensation being transmitted to the driver's foot. Therefore, all of the above options are correct.
10.
Two speed reverse gear arrangement is generally provided in case of
Correct Answer
C. Tractors
Explanation
Two speed reverse gear arrangement is generally provided in tractors. Tractors often require the ability to move in reverse at different speeds depending on the task at hand. This can include tasks such as plowing fields or maneuvering in tight spaces. Having a two speed reverse gear arrangement allows tractors to have more control and flexibility when operating in reverse, making them more efficient and versatile in their use.
11.
Odometer is an instrument used for measurement of
Correct Answer
D. Distance
Explanation
The odometer is an instrument used for measuring distance. It is commonly found in vehicles and displays the total distance traveled by the vehicle. It is an important tool for tracking mileage and determining the wear and tear on a vehicle.
12.
A heat treated glass generally used in automobiles bursts into __________ upon cracking,
Correct Answer
B. Small particles
Explanation
When a heat treated glass used in automobiles cracks, it shatters into small particles instead of sharp-edged fragments. This is because heat treated glass undergoes a process called tempering, where it is heated and then rapidly cooled. This process creates internal stresses in the glass, making it stronger and more resistant to breakage. When the glass does break, these internal stresses cause it to break into small, less dangerous particles instead of large, sharp-edged fragments. This is a safety feature designed to minimize the risk of injury in case of an accident or impact.
13.
In a four wheel drive (4WD), the number of gear boxes are
Correct Answer
B. 2
Explanation
In a four-wheel drive (4WD) vehicle, the number of gearboxes is 2. This is because a 4WD system typically consists of two gearboxes - one for the front wheels and one for the rear wheels. These gearboxes allow power to be transferred from the engine to all four wheels, providing better traction and control in off-road or slippery conditions. Having two gearboxes allows for independent control and distribution of power to each set of wheels, enhancing the vehicle's off-road capabilities.
14.
How many cells are used in a 12 volt car battery ?
Correct Answer
C. 6
Explanation
A 12-volt car battery typically consists of six individual cells, each producing around 2 volts. These cells are connected in series, meaning the positive terminal of one cell is connected to the negative terminal of the next, resulting in a total voltage of 12 volts. Therefore, the correct answer is 6.
15.
An over-inflated tyre will wear the tread most near the
Correct Answer
C. Centre
Explanation
An over-inflated tire will wear the tread most near the center. When a tire is over-inflated, the center of the tread bulges outwards, causing the center of the tire to have more contact with the road surface. This excessive contact leads to increased wear in the center of the tread.
16.
F a tyre is designated as 175/65 R14 82 S, then the aspect ratio for the tyre is
Correct Answer
B. 65
Explanation
The aspect ratio for the tyre is 65. The aspect ratio is the ratio of the height of the tire's cross-section to its width. In this case, the width of the tire is 175 mm and the height is 65% of the width. Therefore, the aspect ratio is 65.
17.
Toe-in ensures parallel rolling of the wheel thus stabilizing steering in addition to preventing both sides slipping and excessive tyre wear.
Correct Answer
A. True
Explanation
Toe-in refers to the inward angle of the front wheels when viewed from above. This alignment technique is used to ensure that the wheels are parallel to each other and perpendicular to the ground. By having a slight toe-in, the wheels are positioned to roll in a straight line when the vehicle is in motion. This helps to stabilize the steering and improve handling. Additionally, toe-in also helps to prevent both sides of the tires from slipping and reduces excessive tire wear. Therefore, the statement is true.
18.
The specific gravity of petrol is about
Correct Answer
A. 0.75
Explanation
The specific gravity of a substance refers to its density compared to the density of water. A specific gravity of less than 1 indicates that the substance is lighter than water. Since petrol has a specific gravity of 0.75, it is lighter than water and will float on its surface.
19.
Which one of the following statement correctly describe the construction of a bevel-gear type differential?
Correct Answer
D. The differential carrier houses differential pinion gears and side gears
Explanation
The correct answer is that the differential carrier houses differential pinion gears and side gears. This means that the differential carrier contains both the pinion gears and side gears of the differential. The pinion gears mesh with the side gears, allowing for the distribution of torque between the two drive shafts. This design allows the left side gear and the differential carrier to rotate at different speeds, providing smooth and efficient power transfer to the wheels.
20.
The brake warning light warns the driver of
Correct Answer
C. Failure of the primary or secondary circuit of hydraulic system
Explanation
The brake warning light is designed to alert the driver of any issues with the hydraulic system in the vehicle's brakes. This includes the failure of either the primary or secondary circuit of the hydraulic system. When either of these circuits fails, it can result in reduced brake performance or a complete loss of braking ability. Therefore, the brake warning light serves as an important safety feature, indicating to the driver that there is a problem with the hydraulic system that needs immediate attention.
21.
Highest useful compression ratio (HUCR) is the highest compression ratio at which the
Correct Answer
D. Fuel can be used in a test engine without knocking
Explanation
The correct answer is "fuel can be used in a test engine without knocking". The highest useful compression ratio (HUCR) refers to the maximum compression ratio at which fuel can be utilized in an engine without causing knocking. Knocking occurs when the air-fuel mixture in the engine's combustion chamber ignites prematurely, leading to inefficient combustion and potential engine damage. Therefore, the HUCR is the compression ratio that allows for the optimal use of fuel without experiencing knocking, ensuring efficient engine performance.
22.
The formula for Iso-octane is
Correct Answer
A. C_{8}H_{18}
Explanation
The correct answer is C8H18. This is because the chemical formula for iso-octane is C8H18, which indicates that it contains 8 carbon atoms and 18 hydrogen atoms. The other options (C7H17, C6H18, C7H18) have different combinations of carbon and hydrogen atoms, which do not match the correct formula for iso-octane.
23.
The function of a governor in automobiles is to
Correct Answer
C. Maintain constant engine speed
Explanation
The function of a governor in automobiles is to maintain a constant engine speed. This is important for several reasons. Firstly, it ensures that the engine operates efficiently and smoothly, reducing the risk of damage or wear. Secondly, it allows for consistent power delivery, which is especially important in applications such as generators or industrial machinery. Additionally, maintaining a constant engine speed can help improve fuel efficiency by optimizing the combustion process. Overall, a governor plays a crucial role in regulating and stabilizing the engine speed to ensure optimal performance and longevity.
24.
Which one of the following statements correctly describes the construction of a planetary gear type differential ?
Correct Answer
B. One drive shaft is splined to the central gear and the other to the planetary gear.
Explanation
The correct answer describes the construction of a planetary gear type differential where one drive shaft is connected to the central gear and the other drive shaft is connected to the planetary gear. This arrangement allows for torque to be distributed between the two drive shafts, providing power to both wheels and allowing them to rotate at different speeds when necessary, such as during turns.
25.
A petrol engine of a car develops 125 N-m torque at 2700 r.p.m. The car is driven in second gear having gear ratio of 1.75. The final drive ratio is 4.11. If the overall transmission efficiency is 90%, then the torque available at the driving wheels is
Correct Answer
C. 809.1 N-m
Explanation
The torque available at the driving wheels can be calculated by multiplying the torque developed by the engine with the gear ratio and the final drive ratio, and then dividing by the overall transmission efficiency. In this case, the torque developed by the engine is 125 N-m, the gear ratio is 1.75, the final drive ratio is 4.11, and the overall transmission efficiency is 90%. Therefore, the torque available at the driving wheels is (125 N-m * 1.75 * 4.11) / 0.9 = 809.1 N-m.
26.
The engine oil viscosity is defined by __________ ratings.
Correct Answer
B. Society of automotive engineers (SAE)
Explanation
The engine oil viscosity is defined by the society of automotive engineers (SAE) ratings. The SAE ratings determine the oil's ability to flow at different temperatures. These ratings are represented by a combination of numbers and letters, such as 10W-30 or 5W-20. The first number indicates the oil's viscosity at low temperatures, while the second number represents its viscosity at high temperatures. This helps vehicle owners choose the right oil for their engine, ensuring optimal performance and protection.
27.
The air resistance to a car at 20 kmph is R. The air resistance at 40 kmph will be
Correct Answer
C. 4R
Explanation
As the speed of the car doubles from 20 kmph to 40 kmph, the air resistance experienced by the car will increase by a factor of 4. This is because air resistance is directly proportional to the square of the velocity. Therefore, the air resistance at 40 kmph will be 4 times the air resistance at 20 kmph, which is represented by 4R.
28.
The boiling point of Diesel fuel is in the range of
Correct Answer
D. 180°C to 360 °C
Explanation
Diesel fuel has a higher boiling point compared to gasoline because it is a heavier and denser fuel. The boiling point of diesel fuel falls within the range of 180°C to 360°C. This means that diesel fuel will start to vaporize and turn into gas at temperatures within this range.
29.
A cycle consisting of one constant pressure, one constant volume and two isentropic processes is known as
Correct Answer
D. Diesel cycle
Explanation
A cycle consisting of one constant pressure, one constant volume, and two isentropic processes is known as the Diesel cycle. This cycle is commonly used in diesel engines, where fuel is injected into the cylinder at constant pressure, followed by a constant volume combustion process. The expansion and compression processes are isentropic, meaning they occur without any heat transfer to or from the system. Overall, the Diesel cycle is an idealized representation of the processes happening in a diesel engine.
30.
There is a loss of heat in an irreversible process.
Correct Answer
A. True
Explanation
In an irreversible process, heat is lost because it cannot be completely converted into work. This is due to factors such as friction, heat transfer to the surroundings, or other irreversibilities. Irreversible processes are characterized by a decrease in the system's entropy, which means that heat is lost to the surroundings, resulting in a loss of energy. Therefore, the statement "There is a loss of heat in an irreversible process" is true.