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Hari Kumar R
Krishna Kumar R
Sangeetha R
Saravanan A
Sruti B
Task 1
CONDUCTIONPop corn cooked with oil in a panOil conducts heat
CONVECTIONPop corn cooked in a popperAir transfers heat
RADIATIONPop corn cooked in a micro-wave ovenMicrowaves break down the bonds
Method Conduction Convection Radiation
Steaming High High Low
Boiling High Moderate Low
Deep frying High Moderate Low
Sautéing High Low Low
Broiling Moderate Low High
Baking High High Moderate
Grilling Moderate Moderate High
Microwaving Low Low High
PERSPIRATIONAmbient temp > body tempEvaporation occursCooling effect of perspiration is due to large
heat of vaporization of water Heat of vaporization = 580 cal/g
CONDUCTION
CONVECTIONHeat transfer medium: air surrounding the
body
Air motion will remove heat from the skin
Increase of heat transfer to the air
Loss due to convection calculated by correlating with loss due to conduction
Conduction and convection together are not adequate for cooling
RADIATION
Cold blooded animals come out in summerTherefore, there are more of insects and
reptiles in the equatorial regionElephant ears act like giant radiators to
transfer heat out of their bodies.
When fans rotate in forward direction It blows the cool air downCan be used in summer
When fans rotate in the reverse directionMakes hot air rise and gently mixes the airCan be used during winter
Hair is partially wetted Oil applied is the conducting medium A metal pressing comb is heated to 300-
500oF The high temperature breaks down the
biochemical disulphide bonds between the keratin proteins
As the hair cools, the broken bonds are fixed in the required shape
This reformation of the bonds holds the hair in its new, straightened shape
A coil of wire is placed beneath the cooking surface
A large ac current is made to flow through the wire
Hence an oscillating magnetic filed is set up
This field induces an electric field when a metal is brought into contact
The eddy resistance in the metal is converted to heat
Coolant is pumped through radiators The radiator transfers the heat from the
fluid inside to the air outside, thereby cooling the engine
Air cooled engines use the air blowing past the engine
But long stationary periods may cause over-heating
Air cooled bikes are cheaper, simpler and lighter than their water-cooled counterparts
Cold water remains at the bottom of the tank as it is denser than hot water
When you first put the water in the coffee maker, the heating element heats it.
Once the coffee is made, the heating element keeps the coffee warm.
Clay is a mixture of mud and water The wet clay pot is heated so that all the
moisture in the wet clay is taken out completely
The whole material is purely porous with very fine holes all over
When you pour water of any temperature more than the room temperature into the pot, the water first spreads itself on to the walls of the pot
Due to the internal pressure of water, the water is forced to contact to the pot inner walls. So the water molecules start filling the air gaps of the pot
In this condition, due to the very fine holes, the water molecules lose their contact and forms in to separate groups of water particles
Since the water volume is very less, it tends to go away from the pothole, and for that is has to be converted in to vapor state. But the temperature of the water is not enough to change its state from liquid to gaseous