Miyav How water becomes steam? Solid Liquid Vapor (air) Low temperature High temperature Phase change heating
Miyav Heat transferred room temperature Heat flows from coffee to room air to reach equilibrium Heat flows from room air to ice cream to reach equilibrium. So ice cream melts why coffee becomes cold after some time?
Miyav Heat transferred room temperature Heat flow High Low to reach thermal equilibrium
Miyav Heat transfer mechanisms The heat is transferred along the body from one particle (molecule) to another without the movement of the particles themselves. This is called as conduction. Conduction (occurs generally in solids)
Miyav Metals are high conductivity material Insulator (conductivity very less) conductor (conductivity very high)
Miyav convection (occurs generally in fluids) The heat is transferred from hotter portions to colder portions by the actual movement of particles of a fluid is called convection.
Miyav Radiation (can occur without any medium) Thermal radiation is the energy radiated from hot surfaces as electromagnetic waves. It does not require medium for its propagation.
Miyav White colour tankers & white gaps Absorption of radiant heat by a body When radiant heat falls on a body a part of it is absorbed by it. There is an increase in its temperature due to this absorption.
Miyav If the surface of a body is painted black it absorbs more heat than when it is painted white. Black roofwhite roof
Miyav How to heat How to “cold” why it is “burning” ?
Miyav Why do we use petrol in aero planes instead of coal for running jet engines?
Miyav 10 Kg of coal 10 Kg of diesel A train can run 1 Km A train can run 4 Km It means that for same amount of mass, diesel produces larger heat compared to coal
Miyav We say that Diesel has high calorific content compared to coal Calorific value of a fuel is the total quantity of heat produced when a unit mass (or volume) of the fuel is burnt completely. Unit of calorific value is kJ/g
Miyav coal diesel High calorific So in scooters, buses, we need to carry less amount of fuel, since the diesel’s calorific value is high petrol wood LPG low calorific High ash zero ash (5) (15) (45) (50) (100) (KJ/g)
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