Presentation on theme: "Methods of Energy Transfer"— Presentation transcript:
1 Methods of Energy Transfer The transfer of heat energy from a hot object can occur in three ways:Conduction is the transfer of energy as heat through a material.Convection is the movement of matter due to differences in density that are caused by temperature variations.Radiation is the energy that is transferred as electromagnetic waves, such as visible light and infrared waves.
2 Methods of Energy Transfer, continued ConductionConduction involves objects in direct contact.Conduction takes place when two objects that are in contact are at unequal temperatures.
3 Methods of Energy Transfer, continued ConvectionConvection results from the movement of warm fluids.During convection, energy is carried away by a heated fluid that expands and rises above cooler, denser fluids.A convection current is the vertical movement of air currents due to temperature variations.
4 Methods of Energy Transfer, continued RadiationRadiation is energy transferred as heat in the form of electromagnetic waves.Unlike conduction and convection, radiation does not involve the movement of matter.Radiation is therefore the only method of energy transfer that can take place in a vacuum.Much of the energy we receive from the sun is transferred by radiation.
5 Conductors and Insulators Any material through which energy can be easily transferred as heat is called a conductor.Most metals are good conductors.
6 Conductors and Insulators Poor conductors are called insulators.Gases are extremely poor conductors.Liquids are also poor conductors.Some solids, such as rubber and wood, are good insulators.
10 A measure of the ability of a material to transfer heat ConductivityA measure of the ability of a material to transfer heat
11 Specific HeatSpecific heat describes how much energy is required to raise an object’s temperature.Specific heat is defined as the quantity of heat required to raise a unit mass of homogenous material 1 K or 1°C in a specified way given constant pressure and volume.Specific Heat Equationenergy = (specific heat) (mass) (temperature change)energy = cmDt