SSC JE General Engineering Online Test in Hindi Series 2024

Self-ignition temperature is the temperature required for the fuel to automatically ignite without the help of external sources like spark plugs or igniter coils. This temperature is also known as kindling point. As petrol ignites with the help of spark plug and diesel by compression. So we don’t require the petrol to reach its self-ignition temperature at an early stage. On the other hand, we need the diesel to reach its self-ignition temperature at an early stage for the combustion purpose. Therefore, the self-ignition temperature of Petrol is kept higher than diesel
Other reasons for keeping the self-ignition temperature of the petrol high is to avoid detonation phenomenon. Detonation is a state where due to certain hot spots or high temperature regions, the petrol ignites automatically before the actual power stroke. It harms the piston, cylinder and decreases your efficiency/mileage of the vehicle.

Benson boiler is a typical high pressure, water tube, forced circulated once through boiler. This boiler does not have any drum.

Specific volume of a substance is the ratio of the substance’s volume to its mass. It is the reciprocal of density.

Weight density is the mass divided by volume. It is more commonly known as density.

Specific gravity is the ratio of the specific weight of the liquid to the specific weight of a standard fluid. In case of liquids standard fluid is taken as water with specific gravity 1.

Viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress.
So correct answer is option C.

COP of refrigerator = Refrigerating effect/ Work input
Refrigerating effect = 360 kJ/min=6 kJ/sec=6 kW
Work input = 2kW
COP = 6/2 = 3

Higher pair: When there is a line or point contact between two elements and the relative motion between them is a combination of sliding and turning. e.g. Toothed gear, belt, rope and chain drive, cam and follower, ball and roller bearing, etc.

Ultimate load is defined as maximum load which can be placed prior to the breaking of the specimen. Stress corresponding to the ultimate load is known as ultimate stress.

When a specimen is loaded beyond the elastic limit the stress increases and reaches a point at which the material starts yielding this stress is called yield stress.

Safe working stress is known as the maximum allowable stress that a material or object will be subjected to when in service. This stress is always lower than the Yield stress and the Ultimate Stress .
Working stress= Yield stress/Factor of safety

Solid state welding is a group of welding processes which produces coalescence at temperatures essentially below the melting point of the base materials being joined, without the addition of brazing filler metal. Pressure may or may not be used. Some examples of solid state welding are (friction welding, ultrasonic welding, forge welding etc.)

The specific heats of gases are generally expressed as molar specific heats. Two specific heats are defined for gases, one for constant volume (C_V) and one for constant pressure (C_P). These two specific heats are related by gas constant(R) as followed

C_P-C_V = R

For cyclic loading conditions endurance strength is considered. Endurance or fatigue limit can be defined as the magnitude of stress amplitude value at or below which no fatigue failure will occur, no matter how large the number of stress reversals takes place. In other words leading to an infinite life to the component or part being stressed. For most ferrous materials Endurance limit (Se) is set as the cyclic stress level that the material can sustain for 10 million cycles.

First understand the knocking in diesel engine. In normal working of diesel engines, initially air is compressed and then the fuel is injected at high pressure. Due to high compression ratio, the fuel ignites and explodes to give the power stroke. Now the requirement of this combustion model is that, the highly atomized fuel should start burning as soon as it is sprayed in the cylinder. But, if the fuel sprayed initially is not able to mix properly due to variety of reasons, it keeps on concentrating in the combustion chamber. This increases the concentration of fuel in the chamber and at some point the large quantity of fuel ignites sending pulses throughout the chamber. This leads to knocking in diesel engine.

Volatility is the ability of a liquid to change to vapor. If a liquid is less volatile then it will not immediately change to vapor in the combustion chamber and thus will increase chances of knocking.
Viscosity is the resistance to flow of the fuel. High viscous fuel will not be easily atomized and mixed. Thus knocking tendency will increase. Similarly if the self-ignition temperature of fuel is high this will cause delay in the ignition and thus knocking will increase.

Fusible plug is fitted to the fire box. It’s object is to put off the fire in the furnace of the boiler when the level of water in the boiler falls to an unsafe limit and avoids the explosion which may takes place due to overheating of the furnace

Cohesion is the tendency of the molecules to stick together and adhesion is tendency of dissimilar particles or surfaces to cling to one another. In case of mercury, the cohesive forces within the drops are stronger than the adhesive forces between the drops and glass. So due to cohesion the mercury does not wet the glass surface.

A gyroscope is a spinning wheel or disc in which the axis of rotation is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum. Because of this, gyroscopes are useful for measuring or maintaining orientation.

In gas welding Heat source is the flame produced by the combustion of a fuel gas and oxygen. Acetylene (C2H2) is the principal fuel gas employed in this welding. No pressure is involved in this welding. Filler metal can be added in the form of a wire or rod.

Rolling contact bearings are also called anti-friction bearing due to its low friction characteristics. These bearings are used for radial load, thrust load and combination of thrust and radial load. e.g Ball bearing, needle bearing etc.

Pelton wheel is a kind of impulse turbine. As in case of impulse turbine pressure throughout turbine is constant and equal to atmospheric pressure, so only energy available for turbine is kinetic energy of fluid. There is no change in pressure energy as it takes place in reaction turbine.

So correct option is A

Rigid Links: Rigid links are those which do not suffer any deformation while transmitting motion. E.g. connecting rod and crank pin

Flexible Links: Flexible links are those which deform appreciably while transmitting motion. E.g. belts, ropes, chain, springs
Fluid Links: When motion is transmitted by means of a fluid. E.g. Hydraulic lift, Hydraulic brake

Intensive property: Whose value is independent of the size or extent i.e. mass of the system. These are, e.g., pressure p and temperature T

Extensive property: Whose value depends on the size or extent i.e. mass of the system (upper case letters as the symbols). e.g., Volume, Mass (V, M). If mass is increased, the value of extensive property also increases. e.g., volume V, internal energy U, enthalpy H, entropy S, etc.
So as per option C Potential energy is extensive as it depends on mass.

The coefficient of restitution is defined as the ratio of relative speeds after and before an impact, taken along the line of the impact. As in perfectly plastic impact there will not be any after impact velocity. So Coefficient of restitution will be zero.