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ELEMENT

ELEMENT. There are 108 elements in nature. STRUCTURE OF AN ATOM. ATOMS ARE THE SMALLEST PARTICLE OF AN ELEMENT THAT SHOWS ITS PROPERTIES. ATOMS ARE BUILDING BRICKS OF ALL MATTER AND MATTER IS ELECTRICAL IN NATURE. AN ATOM CONSIST OF : A) NUCLEUS B) ORBITS. BOHR’S ATOM. BOHR’S ATOM.

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ELEMENT

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  1. ELEMENT There are 108 elements in nature.

  2. STRUCTURE OF AN ATOM ATOMS ARE THE SMALLEST PARTICLE OF AN ELEMENT THAT SHOWS ITS PROPERTIES. ATOMS ARE BUILDING BRICKS OF ALL MATTER AND MATTER IS ELECTRICAL IN NATURE. AN ATOM CONSIST OF : A) NUCLEUS B) ORBITS

  3. BOHR’S ATOM BOHR’S ATOM

  4. NUCLEUS THE CENTRAL PART OF THE ATOM CONTAINS : PROTONS ( + ve CHARGE ) NEUTRONS ( NEUTRAL )

  5. ORBITS • OUTER PART OF THE ATOM CONTAINS ELECTRONS WHICH HAVE A - ve CHARGE. • MASS OF ELECTRON IS NEGLIGIBLE. • CHARGE IS EQUAL AND OPPOSITE TO THAT OF A PROTON. • ATOMIC NO = NO OF PROTONS = NO OF ELECTRONS

  6. ATOM CONSTITUENT SYMBOL CHARGE MASS ELECTRONS E- -1 9.1 X 10-28 G PROTONS P+ +1 1836 X ELECTRON MASS NEUTRONS N 0 APPROXIMATELY THAT OF P+

  7. VALENCE SHELL & FREE ELECTRONS THE OUTER SHELL IS CALLED VALANCE SHELL. ELECTORNS IN OUTER SHELL ARE CALLED FREE ELECTRONS. THESE ELECTRONS CAN BE EASILY DISLODGED FROM THE OUTER SHELL FROM THE ATOM.

  8. ELECTROMOTIVE FORCE • FOR A CHARGE TO FLOW THROUGH, A CONDUCTOR REQUIRES A FORCE. • THIS FORCE IS PROVIDED BY THE POTENTIAL DIFFERENCE APPLIED ACROSS THE TERMINALS.

  9. ALTERNATING CURRENT • THE CURRENT THAT PERIODICALLY CHANGES DIRECTION & CONTINUOUSLY CHANGES MAGNITUDE • IT CAN BE PRODUCED BY : a) STATIONARY COIL AND MOVING MAGNETIC FIELD b) STATIONARY MAGNETIC FIELD AND MOVING COIL

  10. ELECTRICAL FIELD • A CHARGE WHETHER MOVING OR STATIONARY SETS UP AN ELECTRICAL FIELD • STRENGTH OF THE FIELD DEPENDS ON QUANTUM OF CHARGE

  11. RADIO WAVES THE OSCILLATOR IS AN ELECTRONIC DEVICE FOR CREATING VOLTAGES THAT CAN BE MADE TO SURGE BACK AND FORTH AT WHATEVER FREQUENCY IS DESIRED WHEN RF ENERGY IS APPLIED TO A CONDUCTOR (ANTENNA), THE ANTENNA RESONATES (VIBRATES). THE ANTENNA PROVIDES A MEANS OF RADIATING THE ELECTROMAGNETIC (EM) WAVES INTO THE AIR

  12. MAGNETIC FIELD SPEED OF LIGHT = ELECTRICAL FIELD MAGNETIC FIELD THEREFORE MAGNETIC COMPONENT IS VERY SMALL

  13. ELECTROMAGNETIC RADIATION • EACH WAVE PROPAGATES THROUGH SPACE WITH ALTERNATING ELECTRICAL AND MAGNETIC FIELDS. • LIGHT WAVES WITH UV & IR RADIATIONS WERE THE EARLIEST EXAMPLES. • EM WAVES TRAVEL AT THE SPEED OF LIGHT.

  14. PROPAGATION OF EM WAVES • IN FREE SPACE ALL RADIO WAVES & EM WAVES TRAVEL IN A STRAIGHT LINE AT THE SPEED OF LIGHT. • A TYPICAL SINUSOIDAL WAVE WHEN PLOTTED AGAINST TIME GIVES CHANGE IN THE WAVE AMPLITUDE

  15. THE ELECTROMAGNETICSPECTRUM

  16. THE ELECTROMAGNETIC SPECTRUM

  17. THE VISIBLE SPECTRUM

  18. SPECTRUM OF ELECTROMAGNETIC RADIATION REGION λ (ANGS) λ (cm) C (HZ) ENERGY(EV) RADIO > 109 > 10 < 3 X 109 < 10-5 MICRO 109 - 106 10 - 0.01 3 X 109 - 3 X 1012 10-5 - 0.01 INFRARED 106 - 7000 0.01 - 7 X 10-5 3 X 1012 - 4.3 X 1014 0.01 - 2 VISIBLE 7000 - 4000 7 X 10-5 – 4 X 10-5 4.3 X 1014 – 7.5 X 1014 2 - 3 UV 4000 - 10 4 X 10-5 - 10-7 7.5 X 1014 - 3 X 1017 3 - 103 X-RAYS 10 - 0.1 10-7 - 10-9 3 X 1017 - 3 X 1019 103 - 105 GAMMA < 0.1 < 10-9 > 3 X 1019 > 105

  19. TERMS AND DEFINITIONS • 1. CYCLE ONE COMPLETE SERIES OF VALUES OR ONE COMPLETE PROCESS, RETURNING TO VALUES OF ORIGIN. • 2. FREQUENCY (f ) No OF CYCLES/SEC. UNITS ARE HERTZ. • 1 Hz = 1 C/S, 1 K Hz = 10 C/S • 1 M Hz = 10 C/S, 1 G Hz = 10 C/S

  20. TERMS & DEFINITIONS • CYCLE: ONE COMPLETE SERIES OF VALUES OR ONE COMPLETE PROCESS IS ONE CYCLE. • WAVELENGTH : THE PHYSICAL DISTANCE TRAVELLED BY THE WAVE IN ONE CYCLE. • AMPLITUDE : THE MAXIMUM DISPLACEMENT OF THE WAVE ABOUT ITS MEAN POSITION. • FREQUENCY : THE NO OF CYCLES OCCURRING IN ONE SECOND.

  21. PHASE • THE INSTANTANEOUS POSITION OF A PARTICLE IN A WAVE OR POSITION OF A PARTICLE AT A GIVEN TIME • TWO WAVES OF THE SAME FREQUENCY WHEN TRANSMITTED AT THE SAME TIME ARRIVE AT A POINT IN PHASE • PHASE DIFFERENCE IS THE ANGULAR DIFFERENCE BETWEEN THE CORRESPONDING POINTS ON THE WAVEFORMS

  22. PHASE

  23. PHASE DIFFERENCE EXAMPLES

  24. SPEED OF RADIO WAVES SPEED OF LIGHT IS 299,792,458 m/sec WHICH IS APPROX = 3 X 108 m/sec = 162,000 Nm/sec = 186,000 Sm/sec = 300,000 km/sec

  25. POLAR DIAGRAM • IT IS THE LINE JOINING POINTS OF EQUAL INTENSITY AT A GIVEN TIME. OR • A LINE SO PLOTTED THAT IT GIVES THE RELATIVE VALUES OF THE FIELD STRENGTHS OR THE POWER RADIATED AT VARIOUS POINTS IN BOTH HORIZONTAL AND VERTICAL PLANES.

  26. POLAR DIAGRAM

  27. POLARIZATION • ELECTRICAL AND MAGNETIC FIELDS ARE PRODUCED WHEN E/M WAVES TRAVEL THROUGH SPACE • THESE FIELDS ARE AT RIGHT ANGLES TO EACH OTHER • A VERTICAL AERIAL TRANSMITS THE ELECTRICAL FIELD IN A VERTICAL PLANE

  28. POLARISATION POLARISATION ANTENNAS ARE DESIGNED TO PICK UP ELECTRICAL COMPONENT ONLY

  29. CIRCULAR POLARIZATION

  30. CIRCULAR POLARIZATION

  31. MODULATION • PROCESS OF IMPRESSING INTELLIGENCE ON A RADIO CARRIER WAVE (CW) IN ORDER TO CONVEY INFORMATION • VARIOUS TYPE OF MODULATION ARE • (a) KEYING • (b) AMPLITUDE MODULATION • (c) FREQUENCY MODULATION • (d) PULSE MODULATION

  32. NEED FOR MODULATION 1. PRACTICAL ANTENNA HEIGHT: LOWER THE FREQUENCY LARGER THE ANTENNA. 2. OPERATING RANGE : LOWER THE FREQUENCY LOWER THE RANGE. 3. WIRELESS COMMUNICATION : AUDIO FREQUENCIES WHEN TRANSMITTED THROUGH SPACE GET ATTENUATED.

  33. TYPES OF MODULATION • AMPLITUDE MODULATION • FREQUENCY MODULATION • PULSE MODULATION

  34. AMPLITUDE MODULATION THEAMPLITUDEOF THE CARRIER IS CHANGED IN ACCORDANCE WITH THE INTENSITY OF THE SIGNAL THE FREQUENCY OF THE CARRIER WAVE IS KEPT CONSTANT

  35. AMPLITUDE MODULATION

  36. AMPLITUDE MODULATION (AM)

  37. MODULATION DEPTH THE RATIO OF THE AMPLITUDES OF THE SIGNAL TO THE UNMODULATED CARRIER WAVE EXPRESSED IN PERCENTAGE MOD. DEPTH = AMPLITUDE OF SIGNAL *100 AMPLITUDE OF CW

  38. TEMPORAL REPRESENTATIONS OF DSB-AM SIGNALS

  39. IMPORTANCE OF MOD. DEPTH • IF DEPTH LESS THAN 50% - AUDIO SIGNALS NOT VERY STRONG 2. IF DEPTH MORE THAN 75% - AUDIO SIGNALS ARE STRONG AND CLEAR 3. IF DEPTH MORE THAN 100% - DISTORTION IN RECEPTION & WASTAGE OF POWER GREATER THE MODULATION, LESSER THE RANGE

  40. FREQUENCY MODULATION THE FREQUENCY OF THE CARRIER IS CHANGED IN ACCORDANCE WITH THE INTENSITY OF THE AF SIGNAL THE AMPLITUDE OF THE CARRIER WAVE IS KEPT CONSTANT

  41. FM

  42. ADVANTAGES OF FM 1.NOISELESS RECEPTION 2. HIGH EFFICIENCY 3. HI-FI RECEPTION.

  43. DISADVANTAGES OF FM 1. COMPLICATED RECEIVERS 2. OPERATES ON VHF, HENCE RANGE IS LESS.

  44. COMPARISON OF AM AND FM • AMFM • 1. TRANSMITTER COMPLEXSIMPLE • 2. RECEIVER SIMPLE COMPLEX • 3. STATIC EXCESSIVE ALMOST NIL • 4. BAND WIDTHSMALL LARGE • 5. POWER FOR TXLARGE SMALL

  45. SIDE BANDS WHENEVER A CONTINUOUS WAVE IS MODULATED BY A FREQUENCY LOWER THAN ITSELF, ADDITIONAL FREQUENCIES OCCUR ON EITHER SIDE OF THE CW FREQUENCY THESE ARE CALLED SIDE BANDS. THE INTELLIGENCE IS CARRIED IN THESE SIDE BANDS.

  46. AM CW COMPRISES OF CW FREQ CW FREQ + AUDIO FREQ CW FREQ - AUDIO FREQ

  47. AM CW SIDEBANDS

  48. SPECTRAL REPRESENTATIONS OF DSB-AM SIGNALS

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