Home and the work place Conduction The transfer of heat through a solid Particles that make up a substance are vibrating all the time As heat is applied vibrations become more vigorous therefore increasing Kinetic movement Energy ID: 422015
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Slide1
Temperature Control and Ventilation
Home and the work placeSlide2
ConductionThe transfer of heat through a solid.
Particles that make up a substance are vibrating all the time
As heat is applied vibrations become more vigorous, therefore increasing Kinetic (movement) Energy.
Methods of Heat TransferSlide3
In a solid particles are held closely together.If one end of the solid is heated, particles at that end gain energy and vibrate more.
These particles then bump into neighbouring particles and transfer energy causing these particles to then vibrate and so on.
Methods of Heat TransferSlide4
Methods of Heat TransferSlide5
Methods of Heat TransferSlide6
Methods of Heat TransferSlide7
Heat energy is transferred from one place to another by the movement of gas or liquid particles.
When one part of a liquid is heated, particles vibrate more and push each other apart.
So
part of the liquid expands and becomes less dense (lighter) making it rise upwards and it is replaced by cooler liquids which is then heated and raises.
ConvectionSlide8
ConvectionSlide9
These are set up in everyday objects, examples:Hot water tanks. ( students explain)
In a refrigerator, air at the top cabinet is chilled so that it becomes more dense and sinks. Warmer air raises to the top and is chilled and then sinks and so a cooling convection current is set up and the temperature of the air in the frig decreases.
Sea Breeze, this is an example of natural convention currents.
Convection CurrentsSlide10
During the day land heats up more quickly than the sea.
Land heats the air above it which raises and is replaced by colder air from over the sea. This
convection current can be felt as an
onshore breeze blowing from sea onto land.
Convection CurrentsSlide11
At night land cools rapidly,
but the temperature of the sea changes very little. Land becomes cooler than the sea so the air over the sea becomes heated and colder air moves from over the land to over the sea.
The
change in direction produces offshore breeze at night blowing from the land onto the sea.
Convection CurrentsSlide12
Convection CurrentsSlide13
Radiation is the transfer of heat energy by electromagnetic waves. Unlike conduction and convection, radiation does not require fluids, so it is the only way in which heat can be transferred through a vacuum.
RadiationSlide14
RadiationSlide15
A thermostat is used to keep something at a particular temperature.
A bimetallic strip is made from two strips of different metals (iron and brass) riveted together. Both of the metal expand when they are heated, but by different amounts.If the metal is heated the brass expands more than the iron and the metal forms a curve.
The bimetallic strip can be used as a thermostat to keep an electrical iron at the correct temperature.
Thermostats Slide16
ThermostatsSlide17
Students are asked to research and explain the principle by which thermostatically controlled household appliances operate. As in appliances such as electrical and gas ovens and electrical irons
ThermostatsSlide18
Temperature is the measure of the amount of heat energy or the hotness of an object. Temperature is measured using a thermometer.
Liquid-in-glass thermometersUses the expansion of a liquid to measure the change in temperature.
A glass bulb filled with a liquid (mercury or alcohol) is attached with a capillary tube.
The expansion take place because the particles of the liquid gain kinetic energy pushing each other further apart.
Thermometers Slide19
Liquid-in-glass thermometer Slide20
This thermometer is used to measure the temperature of the human body.
Clinical thermometersSlide21
These are used to measure the maximum and minimum temperatures over a period of time.The thermometer contains both mercury and alcohol in a U-shaped tube.
Maximum and Minimum ThermometerSlide22
Maximum and Minimum ThermometerSlide23
These do not use the expansion of mercury to measure the temperature it uses thermal radiation.
Digital thermometerSlide24
Body temperature Human beings are endotherms
and are able to maintain a constant body temperature that is independent of the external environmental temperature. To maintain a constant body temperature heat loss must be equal to heat gain.
Effect of temperature and relative humidity of body functionsSlide25
Heat can be gained by the body from:Cell respiration
Direct radiation from the sun and fires or radiators
Radiation reflected from other surfaces
Conduction from warm surfaces of from consuming hot food or drinkConvection from the surrounding
Effect of temperature and relative humidity of body functionsSlide26
Heat maybe lost from the body by:
Direct radiation when the body is hotter than the environmentConduction to cooler surfaces
Convection to the surrounding
Evaporation of water in sweat
Effect of temperature and relative humidity of body functionsSlide27
Effects of heatSunburn is a condition caused by direct exposure to radiation from the sun. The skin becomes red, blisters occur and eventually the top layers of the skin is peeled off.
Skin cancer caused from the exposure to the sun.
Heat exhaustion caused from too much exposure to the sun.
Heat stroke is a severe condition which occurs when the temperature regulation mechanism breaks down. The sweating mechanism fails.
Effect of temperature and relative humidity of body functionsSlide28
Relative HumidityIt is the measure of the quantity of water vapour in the air.
Warm air can hold more water vapour than cold air because warm air is less dense.
When the air temperature increases the relative humidity decreases.
Relative humidity has an effect on the ability of to loose heat by sweating.
Effect of temperature and relative humidity of body functionsSlide29
Students answerWhat occurs in a dry/hot climate
What occurs in a wet/cold climate
Effect of temperature and relative humidity of body functionsSlide30
The composition of air around us can be changed by:Breathing
Chemical pollutantsPollenDust
Bacteria
Tobacco smokeOdoursThese changes may make us feel hot, sticky, dizzy, give us headaches, and make s less efficient at work. Some pollutants may cause illness such as fever, asthma, even cancer.
Ventilation Slide31
Ventilation maybe simply be:Opening a window
Use of small vents to replace stale airAir conditioning- maybe used to prevent the inside of a building becoming uncomfortably hot. A fan is used to move hot air over a set of cooling coils, the coils contain a fluid called a refrigerant.
Students research the working mechanism of an air conditioning unit.
Ventilation Slide32
Humidifiers These are devises used to increase or maintain the humidity of the air.
Ventilation