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OHM’S LAW FOR DC

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  1. OHM’S LAW FOR DC THE TEMPERATURE REMAINING CONSTANT THE CURRENT FLOWING IN THE CIRCUIT IS DIRECTLY PROPORTIONAL TO THE APPLIED VOLTAGE AND INVERSELY PROPORTIONAL TO ITS RESISTANCE. V = I X R I = V/R R = V/I

  2. NUMERICALS BASED ON OHM’S LAW IF V = 9 VOLT AND R = 10 OHMS I = V/R = 9/10 = 0.9 AMPERE IF I = 10 AMPERE V = 10 VOLT R = I/V = 10 / 10 = 1 OHM IF I = 10 AMPERE R = 5 OHMS V = I * R = 10 * 5 = 50 VOLT

  3. KIRCHHOFF’S FIRST LAW THE TOTAL CURRENT ENTERING THE CUIRCUIT (FLOWING TOWARDS) IS EQUAL TO THE TOTAL CURRENT LEAVING THE CUIRCUIT. KIRCHHOFF’S SECOND LAW THE TOTAL VOLTAGE DROP ACROSS THE RESISTANCE OF A CLOSED CIRCUIT IS EQUAL TO THE TOTAL VOLTAGE APPLIED TO THE CIRCUIT.

  4. DIAGRAM KIRCHHOFF’S FIRST LAW DIAGRAM KIRCHHOFF’S SECOND LAW

  5. POTENTIAL DIFFERENCE IT IS THE AMOUNT OF THE WORK DONE IN BRINGING ONE UNIT OF POSITIVE CHARGE FROM ONE POINT TO ANOTHER IN THE ELECTRIC FIELD. THE VOLTAGE RATING IS MEASURE OF PRESSURE. THE AMOUNT OF PUSH BEHIND ELECTRIC CURRENT (EMF). UNIT IS VOLT

  6. AMPERE THE RATE OF FLOW OF ELECTRON EQUAL TO ONE COULOMB PER SECOND. AMPERE IS UNIT OF CURRENT.

  7. ELECTRIC POWER (WATT) WHENEVER ELECTRIC CURRENT FLOWS WORK IS DONE IN MOVING THE ELECTRONS THROUGH THE CONDUCTOR. THE RATE AT WHICH THE WORK IS DONE IS CALLED POWER. THE BASIC UNIT OF POWER IS WATT. P = V X I OR P = I X I X R 1000 WATT = 1 KILO WATT ( ONE UNIT OF ELECTRICITY IS 1 KW HR ) ONE HORSE POWER = 746 WATTS. ( ENERGY REQUIRED TO LIFT 33000 POUNDS OF WEIGHT TO 1 FEET OF HEIGHT AND KEEP IT THERE FOR 1 MIN.

  8. WATT and DECIBEL 1dB = 10 Log WATT CONVERTING 100 WATT INTO DECIBELS 100 WATT = (10 log 100) dB = 10 *2 = 20 dB 100 WATT = 20 dB, 1000 WATT = 30 dB

  9. JOULE: UNIT OF WORK. ENERGY SPENT IN ONE SECOND BY AN AMPERE FLOWING THROUGH ONE OHM. ENERGY: THE STRENGTH OR CAPACITY REQUIRED TO DO WORK. POWER MEASURED OVER A TIME (KW HR)

  10. RESISTANCE RESISTANCE IS THE OPPOSITION OFFERED BY A MATERIAL TO THE FLOW OF ELECTRON. IN A CIRCUIT RESISTANCE IS USED TO REGULATE FLOW OF CURRENT AND ALSO TO GENERATE HEAT AND LIGHT AT CERTAIN OCCASION THE UNIT OF RESISTANCE IS OHMS. 1000 OHMS = 1 KILO OHMS 1 AMPERE = 1000 MILI AMPERE 1 MICRO VOLT = 1/1 000 000 VOLT

  11. RESISTANCE COLOUR CODE AND CIRCUIT SYMBOL

  12. RESISTANCE COLOUR CODE AND CIRCUIT SYMBOL

  13. RESISTANCE COLOUR CODE B BLACK = 0 B BROWN = 1 R RED = 2 O ORANGE = 3 Y YELLOW = 4 G GREEN = 5 B BLUE = 6 V VOILET = 7 G GREY = 8 W WHITE = 9 B B ROY GREAT BRITAIN VERY GOOD WIFE FIRST AND SECOND COLOUR ARE DIGITS. THIRD COLOUR IS NO OF ZEROS FOURTH COLOUR IS TOLERANCE

  14. RESISTANCE COLOUR CODE B BLACK = 0 B BROWN = 1 R RED = 2 O ORANGE = 3 Y YELLOW = 4 G GREEN = 5 B BLUE = 6 V VOILET = 7 G GREY = 8 W WHITE = 9 FOURTH COLOUR IS TOLERANCE GOLD = 5% SILVER = 10% NO COLOUR = 20% 31 OHMS= FIRST COLOUR WILL BE ORANGE SECOND COLOUR WILL BE BROWN THIRD COLOUR WILL BE BLACK

  15. RESISTANCDE IN SERIES R = R1 + R2 + R3 RESISTANCDE IN PARALLEL 1/R = 1/R1 + 1/R2 + 1/R3

  16. NUMERICALS : RESISTANCE IF R1 = 20 OHMS R2 = 30 OHMS R1 = 40 OHMS IN SERIES R = R1 + R2 + R3 R = 20 + 30 + 40 = 90 OHMS IN PARALLEL 1/R = 1/R1 + 1/R2 + 1/R3 1/R = 1/20 + 1/30 + 1/40 = 6/120 + 4/120 + 3/120 = 13/120 R = 120/13 = 9 OHMS APPROX

  17. An RLC circuit (also known as a resonant circuit, tuned circuit, or LCR circuit) is an electrical circuit consisting of a resistor (R), an inductor (L), and a capacitor (C), connected in series or in parallel. This configuration forms a harmonic oscillator. Tuned circuits have many applications particularly for oscillating circuits and in radio and communication engineering. They can be used to select a certain narrow range of frequencies from the total spectrum of ambient radio waves. For example, AM/FM radios typically use an RLC circuit to tune a radio frequency. Most commonly a variable capacitor allows you to change the value of C in the circuit and tune to stations on different frequencies. Other practical designs vary the inductance L to adjust tuning. An RLC circuit is called a second-order circuit as any voltage or current in the circuit can be described by a second-order differential equation for circuit analysis.

  18. Series RLC Circuit notations: V - the voltage of the power source (measured in volts V) I - the current in the circuit (measured in amperes A) R - the resistance of the resistor (measured in ohms = V/A); L - the inductance of the inductor (measured in henrys = H = V·s/A) C - the capacitance of the capacitor (measured in farads = F = C/V = A·s/V) q - the charge across the capacitor (measured in coulombs C) • Series RLC with Thévenin power source In this circuit, the three components are all in series with the voltage source. • Given the parameters v, R, L, and C, the solution for the charge, q, can be found using Kirchhoff's voltage law. (KVL) gives For a time-changing voltage v(t), this becomes

  19. Parallel RLC Circuit notations: V - the voltage of the power source (measured in volts V) I - the current in the circuit (measured in amperes A) R - the resistance of the resistor (measured in ohms = V/A); L - the inductance of the inductor (measured in henrys = H = V·s/A) C - the capacitance of the capacitor (measured in farads = F = C/V = A·s/V) • Parallel RLC circuit • The complex admittance of this circuit is given by adding up the admittances of the components:

  20. OHM’S LAW FOR AC IMPEDENANCE DESCRIBES A MEASURE OF OPPOSITION TO ALTERNATING CURRENT. IT IS COMBINATION OF RESISTANCE, CAPACITIVE REACTANCE AND INDUCTIVE REACTANCE IT CAN BE CALCULATED BY OHM’S LAW I = E/Z

  21. OHM’S LAW FOR AC RESONANCE IS A SPECIAL FREQUENCY IN AC CIRCUIT DETERMINED BY VALUE OF RESISTANCE , CAPACITANCE AND INDUCTANCE. IN SERIES RESONANCE IS GIVEN BY MINIMUM IMPEDENCE AND ZERO PHASE. IN PARALLEL ROSONANCE IN MAXIMUM, WHEN INDUCTANCE AND CAPCITANCE ARE EQUAL AND 180 OUT OF PHASE. IT CAN BE CALCULATED BY F = ½ PI UNDERROOT LC

  22. IMPEDENANCE DESCRIBES A MEASURE OF OPPOSITION TO ALTERNATING CURRENT IT IS COMBINATION OF RESISTANCE, CAPACITIVE REACTANCE AND INDUCTIVE REACTANCE IT CAN BE CALCULATED BY OHM’S LAW I = E/Z

  23. FUSE IT IS CURRENT RATED. IT IS INSERTED BETWEEN ELECTRICAL SUPPLY AND EQUIPMENT TO PROTECT IT FROM GETTING DAMAGED. IF CURRENT FLOW IN THE CIRCUITS EXCEEDS THE RATING. IF EQUIPMENT NEEDS 500 M A FUSE ( ½ A) IS INSERTED. CIRCUITS BREAKER ARE ALSO USED AS PROTECTION FROM OVER LOADS. IF CURRENT INCREASES, IT JUMPS AND BREAKS THE CIRCUIT.

  24. CELL • CELL IS A DEVICE WHICH CONVERTS CHEMICAL ENERGY INTO DIRECT CURRENT • COMBINATION OF CELLS IS KNOWN AS BATTERY • CELLS CAN BE CONNECTED IN SERIES OR PARELLEL • SERIES : VOLTAGE ADDS UP CURRENT REMAINS THE SAME • PARALLEL : CURRENT ADDS UP VOLTAGE REMAINS THE SAME

  25. RATING OF A BATTERY • BATTERIES ARE RATED IN AMPERE HOUR (AH) • 5 AH BATTERY CAN GIVE CURRENT OF 1 AMPERE FOR 5 HOURS OR 5 AMPERE FOR 1 HOUR. BUT IT CAN NOT GIVE 10 AMPERE FOR HALF HOUR DUE TO BATTERY INTERNAL RESISTANCE

  26. CIRCUIT DIAGRAM CELL

  27. TYPES OF CELLS : PRIMARY • DRY CELLS ARE KNOWN AS PRIMARY CELLS • VOLTAGE IS 1.5 VOLT (ONE TIME USE TYPE) • CARBON ROD IS +VE • CONTAINER IS ZINC –VE • AMMONIUM CHLORIDE IS ELECTROLYTE • ADVANTAGE : CHEAP TO MASS PRODUCE • DISADVANTAGE : CAN NOT BE RECHARGED AND IF LEFT UNUSED FOR SOME TIME, IT DETORIATES

  28. CELLS : SECONDARY CELL • SECONDARY CELLS CAN BE RE CAHRGED • TWO TYPES OF SECONDARY CELLS ARE • LEAD ACID • NICKEL CADMIUM

  29. SECONDARY CELLS : LEAD ACID • VOLTAGE IS 2 VOLT • LEAD PEROXIDE IS +VE • LEAD OXIDE IS –VE • DILUTED SULPHURIC ACID IS ELECTROLYTE • SPECIFIC GRAVITY WHEN CHARGED 1.25 TO 1.35 • SPECIFIC GRAVITY WHEN DISCHARGED FALLS TO 1.17. • SPECIFIC GRAVITY IS MEASURED BY HYDROMETER • TOPPING UP IS DONE BY DISTILLED WATER

  30. LEAD ACID : ADVANTAGE / DISADVANTAGE • ADVANTAGE • CAN BE RECAHRGED • DISADVATAGE • BATTERIES DISCHARGES IF KEPT UNUSED FOR A LONG TIME • CHARGING HAS TO BE CAREFULLY MONITORED BY CHECKING VOLTAGE AND SPECIFIC GRAVITY • OVERCHARGING IS A PROBLEM • BOTH VOLTAGE AND SPECIFIC GRAVITY IS CHECKED FOR DETERMINING IF A BATTERY IS DISCHARGED.

  31. SECONDARY CELLS : NICKEL CADMIUM • VOLTAGE IS 1.2 VOLT UNDER VARYING LOAD • NICKEL HYDROXIDE IS +VE • CADMIUM IS –VE • POTTASIUM HYDROXIDE (KOH) IS ELECTROLYTE

  32. NICKEL CADMIUM : ADVANTAGE / DISADVANTAGE • ADVANTAGE • RUGGED, NON SPILLABLE • NOT DAMAGED IF UNUSED FOR A LONG TIME • OVER CHARGING AND DISCHARGING DOES NOT AFFECT MUCH • USED IN AIRCRAFT

  33. INVERTOR • AN INVERTOR IS AN ELECTRONIC DIVICE TO CONVERT DC TO AC • BATTERY POWER IS USED FOR EMERGENCY SUPPLY • BATTERY OUTPUT WHICH IS DC IS CONNECTED TO INVERTOR. THE OUTPUT IS FED TO EQUIPMENTS

  34. INDUCTOR • A COIL OF WIRE USED TO SUPPLY INDUCTANCE IN THE CIRCUIT. • VOLTAGE WHICH IS GENERATED IS CALLED INDUCED EMF • INDUCED EMF OPPOSES ANY CHANGE IN THE CURRENT WHICH INDUCED IT. • UNIT IS HENRIES AND SYMBOL IS L • SERIES : L = L1 + L2 + L3 • PARALLEL : L = 1/L1 + 1/L2 + 1/L3

  35. INDUCTOR INDUCTOR IN SERIES L = L1 + L2 + L3 RESISTANCDE IN PARALLEL 1/L = 1/L1 + 1/L2 + 1/L3

  36. NUMERICALS : INDUCTOR IF L1 = 20 HENERIES L2 = 30 HENERIES L1 = 40 HENERIES IN SERIES L = L1 + L2 + L3 L = 20 + 30 + 40 = 90 HENERIES IN PARALLEL 1/L = 1/L1 + 1/L2 + 1/L3 1/L = 1/20 + 1/30 + 1/40 = 6/120 + 4/120 + 3/120 = 13/120 L = 120/13 = 9 HENERIES APPROX

  37. CAPACITOR • TWO CONDUCTING PLATE SEPERATED BY INSULATING MATERIAL (DIEELECTRIC) CONSTITUTES A CAPACITOR • AC WILL FLOW NOT DC • UNIT IS FARAD • SERIES : 1/ C = 1/C1 + 1/C2 + 1/C3 • PARALLEL : C = C1 + C2 + C3 • IN VARIABLE AIR CAPACITOR AIR IS DIELECTRIC • F = 1 / 2R UNDER ROOT LC