An air conditioner is able to cool a building because it removes heat from the indoor air and transfers it outdoors. A chemical refrigerant in the

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2 An air conditioner is able to cool a building because it removes heat from the indoor air and transfers it outdoors. A chemical refrigerant in the system absorbs the unwanted heat and pumps it through a system of piping to the outside coil.... Most central air conditioning units operate by means of a split system.

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5 Fuses The fuse or circuit breaker protects the airconditioning and heating components including wiring, and usually has a rating of 20 to 30 A. Two types of fuses are currently being used in domestic automobiles. One type consists of a thin ribbon of flat wire, which is enclosed in a glass tube with metal ends The other type is also a thin ribbon of flat wire, but is enclosed in a plastic case and has metal ends. One type is not replaceable with other.

6 Master Control The master control generally includes provisions for the blower speed control, and a rheostat. A variable resistor is used for speed control. A four-speed control circuit uses three internal resistors to control motor speed. Greatest resistance in the circuit results in a low speed and no resistance results in a high speed.

7 Thermostat Thermostat, a means of temperature control, is used for the control of the electromagnetic clutch of the compressor. It is basically an electrical switch, which is actuated by a change in temperature. It senses either evaporator core temperature or the temperature of the refrigerant as it enters or leaves the evaporator.

8 Blower Motor Many types of blower motors are in use, depending upon the application. They may be flange mounted and may have provisions for internal cooling. The blower motor drives one or two squirrel-cage blowers (Fig ) to move air across the evaporator and/or heater core

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10 Your air conditioner has three primary parts that are responsible for changing the state of refrigerant in order to cool your home The evaporator, condenser and compressor. The compressor plays a critical role in the cooling process because it is the middle-man between the evaporator inside your home and the condenser outside your home.

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12 The job of the compressor is to convert the lowpressure, gaseous refrigerant from the evaporator into a high-pressure, hightemperature gas before it enters the condenser.

13 condenser is a device or unit used to condense a substance from its gaseous to its liquid state, by cooling it. In so doing, the latent heat is given up by the substance and transferred to the surrounding environment. Condensers can be made according to numerous designs

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15 An Electric Locomotive is a railway vehicle that can move along rails and push or pull a train attached to it using electric power drawn from an external source, usually from overhead cables or a third rail. Electric Locomotives do not have a conventional engine in them, but use the electricity collected from the outside source to power traction motors which turn the wheels.

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17 A Diesel Locomotive is a self-powered railway vehicle that moves along the rails and pulls or pushes a train attached to it using a huge internal combustion engine running on Diesel fuel as the prime mover or the primary supplier of power..

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19 Unlike conventional automobiles, modern diesel locomotives have no direct mechanical connection between the engine and the wheels, hence the power generated by the engine does not really turn the wheels. Instead, the diesel engine is used to turn a huge electricity generator /alternator which produces electric current (earlier Direct Current, nowadays Alternating Current), which is then transmitted to traction motors which then produce the actual (rotational) torque that turns the wheels of the locomotive

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21 All objects are emitting and absorbing EM radia-tion. Consider a iron rod placed in a fire. As heating occurs, the emitted EM waves have higher energy and eventually become visible. First red... then white Light may be defined as electromagnetic radiation that is capable of affecting the sense of sight.

22 E B c 3 x 10 8 m/s Wave Properties: 1. Waves travel at the speed of light c. 2. Perpendicular electric and magnetic fields. 3. Require no medium for propagation. Electric E Magnetic B For a complete review of the electromagnetic properties, you should study module 32C.

23 The electromagnetic spectrum spreads over a tremendous range of frequencies or wavelengths. The wavelength l is related to the frequency f: c = fl c = 3 x 10 8 m/s Those EM waves that are visible (light) have wave-lengths that range from to cm. Red, l cm Violet, l cm

24 Frequency wavelength f (Hz) l ( nm) Gamma rays X-rays Ultraviolet Infrared rays Short Radio waves Broadcast Radio Long Radio waves A wavelength of one nanometer 1 nm is: 1 nm = 1 x 10-9 m Red 700 nm Violet 400 nm c = fl Visible Spectrum 400 nm 700 nm c = 3 x 10 8 m/s

25 The Helium Neon Laser Laser Wavelength l = 632 nm c c f l f l 8 3 x 10 m/s x 10 m f = 4.75 x Hz Red light

26 Any study of the nature of light must explain the following observed properties: Rectilinear propagation: Light travels in straight lines. Reflection: Light striking a smooth surface turns back into the original medium. Refraction: Light bends when entering a transparent medium.

27 Physicists have studied light for centuries, finding that it sometimes behaves as a particle and sometimes as a wave. Actually, both are correct! Reflection and rectilinear propagation (straight line path) Dispersion of white light into colors.

28 Light may be thought of as little bundles of waves emitted in discrete packets called photons. photons The wave treatment uses rays to show the direction of advancing wave fronts. Light ray Light rays are convenient for describing how light behaves.

29 A geometric analysis may be made of shadows by tracing light rays from a point light source: Point source shadow screen The dimensions of the shadow can be found by using geometry and known distances.

30 h 80cm 4cm 20cm The ratio of shadow to the source is same as that of ball to source. Therefore: 4 cm h 20 cm 80 cm h (4 cm)(80 cm) 20 cm h = 16 cm

31 penumbra Extended source umbra The umbra The umbra is the is region the region where where no light no reaches light reaches the screen. the screen. The penumbra is the outer area where only part of the light reaches the screen.

32 Sensitivity Human eyes are not equally sensitive to all colors. Sensitivity curve 555 nm Eyes are most sensi- tive in the mid-range near l = 555 nm. 400 nm 700 nm Wavelength l 40 W 40 W Yellow light appears brighter to the eye than does red light.

33 Luminous flux is the portion of total radiant power that is capable of affecting the sense of sight. Typically only about 10% of the power (flux) emitted from a light bulb falls in the visible region. The unit for luminous flux is the lumen which will be given a quantitative definition later.

34 Working with luminous flux requires the use of a solid angle measure called the steradian (sr). A solid angle of one steradian (1 sr) is subtended at the center of a sphere by an area A equal to the square of its radius ( R 2 ). R A The Steradian W W A R 2

35 R 5 m W The Steradian W A 1.6 m 2 A R 2 W W A R W = sr m (5.00 m) 2

36 One lumen (lm) is the luminous flux emitted from a 1/60 cm 2 opening in a standard source and included in a solid angle of one steradian (1 sr). In practice, sources of light are usually rated by comparison to a commercially prepared standard light source. A typical 100-W incandescent light bulb emits a total radiant power of about 1750 lm. This is for light emitted in all directions.

37 Recalling that luminous flux is really radiant power allows us to define the lumen as follows: One lumen is equal to 1/680 W of yellow-green light of wavelength 555 nm. A disadvantage of this approach is the need to refer to sensitivity curves to determine the flux for different colors of light. Sensitivity curve Wavelength l

38 The luminous intensity I for a light source is the luminous flux per unit solid angle. Luminous intensity: W F I W F I W Unit is the candela (cd) A source having an intensity of one candela emits a flux of one lumen per steradian.

39 An isotropic source emits in all directions; i.e., over a solid angle of 4p steradians. W = 4p sr Thus, for such a source, the intensity is: I F W F 4p Total flux: F = 4pI The flux confined to area A is: F = I A W R 3 m

40 Total flux: F = 4pI F T = 4p(30 cd) = 377 lm The luminous intensity of the beam depends on W. W R 3 m A W W R (3 m) m 2 2 ; sr I F W 754 lm sr Beam Intensity: I = 8490 cd

41 The illumination E of a surface A is defined as the luminous flux per unit area (F/A) in lumens per square meter which is renamed a lux (lx). An illumination of one lux occurs when a flux of one lumen falls on an area of one square meter. Illumination, E W R E F A Unit: lux (lx) Area A

42 The illumination E of a surface is directly proportional to the intensity I and inversely proportional to the square of the distance R. F F E ; I ; F IW A W IW A E but W so that 2 A R Illumination, E I R 2 W Area A This equation applies for perpendicular surfaces. R

43 E I R 400 cd (2.40 m) 2 2 W R Illumination: E = 69.4 lx Now, recalling that E = F/A, we find F from: F = EA = (69.4 lx)(1.20 m 2 ) F = 93.3 lm

44 E I R 2 E/4 E/9 9 m 2 E 4 m 2 1 m 1 m 2 2 m 3 m If the intensity is 36 lx at 1 m, it will be 9 lx at 2 m and only 4 lx at 3 m.

45 Light may be defined as electromagnetic radiation that is capable of affecting the sense of sight. General Properties of Light: Rectilinear propagation Reflection Refraction c = fl c = 3 x 10 8 m/s Red, l 700 nm Violet, l 400 nm

46 The formation of shadows: penumbra Extended source umbra Luminous flux is the portion of total radiant power that is capable of affecting the sense of sight.

47 R W A Luminous intensity: F I W The Steradian Total flux: F = 4pI W A R 2 Unit is the candela (cd) F E Unit: lux (lx) A

48 Illumination, E I R 2 Illumination, E 9 m 2 E/9 E/4 W R 4 m 2 E 3 m 2 m 1 m 2 1 m Area A

49 Thank You