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STRUCTURE OF AN ATOM

STRUCTURE OF AN ATOM. THERE ARE 108 ELEMENTS IN NATURE 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. NUCLEUS.

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STRUCTURE OF AN ATOM

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  1. STRUCTURE OF AN ATOM • THERE ARE 108 ELEMENTS IN NATURE • 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

  2. BOHR’S ATOM

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

  4. 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

  5. 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+

  6. VALENCE SHELL & FREE ELECTRONS THE OUTER SHELL IS CALLED VALANCE SHELL. ELECTORNS IN OUTER SHELL ARE CALLED FREE ELECTRONS. THESE ELECTRONS IN OUTER SHELL CAN BE EASILY DISLODGED. THE NUMBER OF ELECTRONS WHICH CAN BE ACCOMODATED IN ANY ORBIT IS 2 N SQUARE, WHERE N IS NUMBER OF ORBIT. SO IN THIRD ORBIT WE CAN ACCOMMODATE 2 * 3 * 3 = 18 ELECTRONS

  7. VALENCE SHELL & FREE ELECTRONS IF THE OUTER SHELL THAT IS VALANCE SHELL CONTAINS MORE THAN FOUR ELECTRONS WE CALL IT CONDUCTOR. EXAMPLE IF THE OUTER SHELL THAT IS VALANCE SHELL CONTAINS LESS THAN FOUR ELECTRONS WE CALL IT INSULATOR. EXAMPLE IF THE OUTER SHELL THAT IS VALANCE SHELL CONTAINS MORE THAN FOUR ELECTRONS WE CALL IT SEMI CONDUCTOR. EXAMPLE

  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. THE ELECTROMAGNETICSPECTRUM

  11. THE ELECTROMAGNETIC SPECTRUM

  12. THE VISIBLE SPECTRUM

  13. 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 SPECTRUM OF ELECTROMAGNETIC RADIATION

  14. RADIO WAVES RADIO WAVE IS AN ELECTRO-MAGNETIC WAVE WHICH HAS ELECTRICAL AND MAGNETIC COMPONENT PERPENDICULAR TO EACH OTHER. IN FREE SPACE ALL RADIO WAVES & EM WAVES TRAVEL IN A STRAIGHT LINE AT THE SPEED OF LIGHT. ITS FREQUENCY IS FROM 3 K Hz TO 300 G Hz

  15. Table of ITU Radio Bands Symbols Frequency Range Wavelength Range Typical sources 1 ELF 3 to 30 Hz 10,000 to 100,000 km deeply-submerged submarine communication 2 SLF 30 to 300 Hz 1000 to 10,000 km submarine communication, ac power grids 3 ULF 300 to 3 kHz 100 to 1000 km earth quakes, earth mode communication 4 VLF 3 to 30 kHz 10 to 100 km near-surface submarine communication, 5 LF 30 to 300 kHz 1 to 10 km AM broadcasting, aircraft beacons 6 MF 300 to 3000 kHz 100 to 1000 m AM broadcasting, 7 HF 3 to 30 MHz 10 to 100 m Skywave long range radio communication 8 VHF 30 to 300 MHz 1 to 10 m FM radio broadcast, television broadcast, DVB-T, MRI 9 UHF 300 to 3000 MHz 10 to 100 cm microwave oven, television broadcast, GPS, mobile phone communication (GSM, UMTS, 3G, HSDPA), cordless phones (DECT), WLAN (Wi-Fi), Bluetooth 10 SHF 3 to 30 GHz 1 to 10 cm DBS satellite television broadcasting, WLAN (Wi-Fi), WiMAX, radars 11 EHF 30 to 300 GHz 1 to 10 mm directed-energy weapon (Active Denial System), Security screening (Millimeter wave scanner), intersatellite links, WiMAX, high resolution radar

  16. VLF  Very Low Frequency  3 kHz  30 kHz VF  Voice Frequency  300 Hz  3 kHz ELF  Extremely low Frequency  30 Hz  300 Hz ULF  Ultra Low Frequency  3 Hz  30 Hz

  17. OSCILLATOR 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

  18. TYPES OF OSCILLATOR MASTER OSCILLATOR CRYSTAL OSCILLATOR BEAT FREQUENCY OSCILLATOR LOCAL FREQUENCY OSCILLATOR

  19. PHOTO OF OSCILLATOR

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

  21. 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

  22. 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.

  23. RELATIONSHIP BETWEEN FREQUENCY WAVELENGTH FREQUENCY ( f ) Hz = SPEED OF LIGHT ( c ) METERS/SEC WAVE LENGTH ( l ) METERS WAVE LENGTH ( l ) = SPEED OF LIGHT ( c ) METERS/SEC FREQUENCY ( f ) Hz

  24. RELATIONSHIP BETWEEN FREQUENCY WAVELENGTH FOR CALCULATION PURPOSE CONVERT FREQUENCY INTO METERS AND WAVE LENGTH INTO METERS UNIT OF FREQUENCY I CYCLE PER SECOND = 1 Hz 1000 Hz = 1 KILO Hz 1000 K Hz = 1 MEGA Hz 1000 M Hz = 1 GIGA Hz 100 CM = 1 METERS

  25. RADIO SPECTRUM ABREVIATION FREQUENCYWAVELENGTH VLF 3 - 30 K Hz 100 - 10 km LF 30 - 300 K Hz 10,000 - 1000 m MF 300 - 3000 K Hz 1000 - 100 m HF 3 - 30 M Hz 100 - 10 m VHF 30 - 300 M Hz 10 - 01 m UHF 300 - 3000 M Hz 100 - 10 cm SHF 3000 - 30000 M Hz 10 - 01 cm EHF 30000 - 300000 MHz 1 - 0.1 cm

  26. 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

  27. PHASE

  28. PHASE DIFFERENCE EXAMPLES

  29. 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 EFRACTIVE INDEX IS RATIO OF SPEED OF LIGHT IN A MEDIA AND SPEED OF LIGHT IN VACCUM SPEED OF RADIO WAVE IS MOST IN VACCUM SPEED OF RADIO WAVE IS MORE OVER WATER THAN LAND

  30. 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.

  31. POLAR DIAGRAM

  32. 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

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

  34. 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

  35. 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.

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

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

  38. AMPLITUDE MODULATION

  39. AMPLITUDE MODULATION (AM)

  40. 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

  41. TEMPORAL REPRESENTATIONS OF DSB-AM SIGNALS

  42. 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

  43. 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

  44. FM

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

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