DIFFERENCE BETWEEN EXTENSIVE PROPERTIES AND INTENSIVE PROPERTIES EXPLAINED !!

Any characteristic of a system is called property. For example: pressure, temperature, volume and mass are some familiar properties of a system. Viscosity, thermal conductivity, modulus of elasticity thermal expansion coefficient, electrical resistivity etc are less familiar properties.Any property may be either intensive or extensive.

Intensive property 

1. It is the property of matter that is independent of the quantity of the substance 
2. The density of single drop of water is same as the density of 5 or 10 litres of water 
3. Eg: density, specific gravity, temperature etc 

So we can say that Intensive properties refer to properties that are independent compared to the size or quantity of the substance. These properties do not change when more of a substance is added or some of the substance is removed. Intensive properties include: density, color, viscosity, electrical resistivity, spectral absorption, hardness, melting point/boiling point, pressure, ductility, elasticity, malleability, magnetization, concentration, temperature and magnetic field.

These properties do not change if the size of the quantity of the substance changes. For example: the hardness of a diamond does not change, no matter how many times the diamond is cut. The color of the salt does not change no matter how much of it is added to the original amount. These all describe the intensive properties of the diamond and salt.

Extensive property 

1. It is the property of matter that is dependent of the quantity of the substance 
2. There is an obvious difference between 1 g of sugar and 1 Kg of sugar both in quantity and value. 3. Eg: Mass, volume etc 

So we can say that Extensive properties refer to properties that are dependent on the size or quantity of the substance. These properties change depending on how much of the substance is added or removed. The value of the additive property is proportional to the size of the system. For example if the size is increased, then the property will also increase. Extensive properties include: energy, entropy, mass, length, particle number, number of moles, volume, magnetic moment, weight and electrical charge.

These properties are directly proportional to the size and the quantity of the substance. For example: if the amount of water increases, the weight of the water will also increase; the more the water, the heavier it will be. Another example: the energy it would take to melt an ice cube is proportional to its size. The energy it would take to melt and ice cube differs from the energy that would be required to melt an iceberg.

CHECK OUT WHY DOES A 100CC BIKE HAVE A 140KM/H SPEEDOMETER WHILE ITS TOP SPEED ONLY 80-90KM/H !!

The actual reason is VISIBILITY.

Lets consider a standard analog speedometer.

Even though the bike has top speed of about 70–75kmph. Even downhill speed may go up to 90kmph (when gear is engaged, even downhill speed is controlled by highest engine speed). The speedometer is marked up to 120kmph. The reason is, if the speedometer was marked only up to 80–90kmph, the needle would point extreme right. The time taken to find that needle by the user and register the corresponding number value in the mind would be quite high. At the same time, in the current set-up, the needle is dead in the middle. i.e. we can see it and understand the situation much faster. This time gap may be the difference between a near miss and accident.

Even in a circular speedometer as given below,

The speedometer and tachometer, both have similar concept. You are supposed to shift up when the tachometer needle is at center. Similarly, the speed is above normal if the needle is straight or above straight in the speedometer.

Even in industrial gauges, we set the middle as green region, left and right as red region. So whenever there is inspection, all the inspector has to check is if the needle is straight or not. If it is straight, it is OK. Otherwise, Not OK. Simple.

DIFFERENCE BETWEEN KNOCKING AND DETONATION EXPLAINED !!

Both knocking and detonation means sudden increase in pressure inside the cylinder of engine.But,there is a small difference in the way at which they take place.

In a spark ignition engine combustion which is initiated between spark plug electrodes spreads across the combustible mixture. A definite flame front which seperates the fresh charge from the products of combustion travels from spark plug to the other end of combustion chamber. In order to effect pressure equilisation the burned part of the mixture expand, and compresses the unburned mixture adiabatically increasing its pressure and tempetature, The process continues as the flame front advances through the mixture and the tempereture and pressure of the unburned mixture are increased furthur.

If the temperature of unburnt mixture exceeds the self Ignition temperature of the fuel and remains at or above this temperature during the period of pre-flame reactions auto Ignition occurs.This auto-ignition results in sudden rise in pressure.THIS PHENOMENON IS CALLED KNOCKING.This is also called auto-ignition because it is initiated automatically with very less control. 

In diesel engines,during the cold starting conditions a situation might arise in which the vaporization of fuel is limited due to cold combustion chamber. Low vaporization result in misfiring or no combustion at all in cylinders. This results in accumulation of fuel inside combustion chamber. This fuel after certain cycle then burns rapidly, producing tremendous power. This might occur while the engine is in start of compression stroke or exhaust stroke. Hence producing huge stresses within the engine. This phenomenon is called detonation

So in short, knocking occurs in spark ignition (petrol engine) due to auto-ignition of fuel resulting in sudden rise in pressure whereas detonation occurs in compression ignition engine (diesel engine) due to sudden burning of accumulated fuel particles resulting in sudden increase in pressure.