Module 04 Electronic 100 Important Sentences for Revision

1. Basics of Electronics

1. Electronics deals with the flow of electrons in vacuum, gas, or semiconductor.
2. Current flow in electronics is controlled using components.
3. Electric current is the movement of free electrons in a circuit.
4. Voltage is the potential difference that drives current.
5. Resistance limits the amount of current in a circuit.
6. Conductors allow easy flow of electrons.
7. Insulators resist the flow of electrons.
8. Semiconductors have conductivity between conductors and insulators.
9. Silicon and germanium are common semiconductor materials.
10. Doping adds impurities to semiconductor to change its properties.

2. Types of Current

11. Direct current (DC) flows in one direction only.
12. Alternating current (AC) changes direction periodically.
13. DC voltage is constant over time.
14. AC voltage varies sinusoidally with time.
15. Frequency is the number of AC cycles per second.
16. Frequency is measured in hertz (Hz).
17. Period is the time taken for one complete AC cycle.
18. The RMS value of AC gives equivalent DC value.
19. Peak value is the maximum value of an AC waveform.
20. Average value of AC equals 0.637 × peak value.

3. Conductors, Resistors, and Materials

21. Ohm’s law states V = I × R.
22. Resistance increases with temperature in most metals.
23. Resistivity depends on material type and temperature.
24. Conductivity is the reciprocal of resistivity.
25. Colour codes identify resistor values.
26. Fixed resistors have constant resistance.
27. Variable resistors allow resistance adjustment.
28. Potentiometers act as voltage dividers.
29. Thermistors change resistance with temperature.
30. LDRs (Light Dependent Resistors) change resistance with light intensity.

4. Capacitors

31. Capacitor stores electrical energy in an electric field.
32. Capacitance is the ability to store charge.
33. Unit of capacitance is the farad (F).
34. Capacitance increases with plate area and decreases with plate distance.
35. Dielectric material increases capacitor’s efficiency.
36. Energy stored in a capacitor = ½ C × V².
37. Capacitor blocks DC and allows AC to pass.
38. Electrolytic capacitors are polarized.
39. Ceramic capacitors are non-polarized.
40. Capacitors are used for filtering, timing, and coupling circuits.

5. Inductors

41. Inductor stores energy in a magnetic field.
42. Inductance opposes change in current flow.
43. Unit of inductance is the henry (H).
44. Inductance increases with more coil turns.
45. Inductance increases with iron or ferrite core.
46. Inductive reactance increases with frequency.
47. Formula for inductive reactance: XL = 2πfL.
48. Inductors are used in filters and tuned circuits.
49. Mutual inductance occurs between two nearby coils.
50. Energy stored in inductor = ½ L × I².

6. AC Circuits

51. In resistive circuit, voltage and current are in phase.
52. In inductive circuit, current lags voltage by 90 degrees.
53. In capacitive circuit, current leads voltage by 90 degrees.
54. Impedance (Z) is total opposition to AC current.
55. Impedance combines resistance and reactance.
56. Formula: Z = √(R² + (XL − XC)²).
57. Power factor = cos φ, where φ is phase angle.
58. True power = V × I × cos φ.
59. Apparent power = V × I.
60. Reactive power = V × I × sin φ.

7. Diodes

61. A diode allows current to flow in one direction only.
62. It has an anode and a cathode terminal.
63. P-N junction forms when p-type and n-type materials join.
64. Forward bias allows current to pass through diode.
65. Reverse bias blocks current flow.
66. Silicon diode forward voltage drop is about 0.7 V.
67. Germanium diode forward voltage drop is about 0.3 V.
68. Zener diode operates in reverse breakdown region for voltage regulation.
69. LED emits light when forward biased.
70. Photodiode generates current when exposed to light.

8. Rectifiers and Power Supplies

71. Rectifiers convert AC voltage into DC voltage.
72. Half-wave rectifier uses one diode.
73. Full-wave rectifier uses two or four diodes.
74. Bridge rectifier uses four diodes in bridge configuration.
75. Filter capacitor smooths pulsating DC output.
76. Ripple voltage is unwanted AC variation in DC output.
77. Voltage regulators maintain constant DC output.
78. Linear regulator dissipates excess voltage as heat.
79. Switching regulator uses high-frequency switching for efficiency.
80. Power supply converts and stabilizes electrical power for circuits.

9. Transistors

81. Transistor is a three-terminal semiconductor device.
82. Terminals are emitter, base, and collector.
83. NPN and PNP are two transistor types.
84. Small base current controls large collector current.
85. Transistor acts as amplifier or switch.
86. Current gain (β) = collector current / base current.
87. In common emitter configuration, output is inverted.
88. Biasing sets correct operating point of transistor.
89. Saturation means transistor fully conducts.
90. Cut-off means transistor completely off.

10. Digital Electronics and Logic Gates

91. Digital signals have two states: ON (1) and OFF (0).
92. Analog signals vary continuously.
93. Logic gates perform basic digital operations.
94. AND gate output is 1 only if all inputs are 1.
95. OR gate output is 1 if any input is 1.
96. NOT gate output is opposite of input.
97. NAND gate output is opposite of AND output.
98. NOR gate output is opposite of OR output.
99. XOR gate output is 1 when inputs are different.
100. Digital electronics form the basis of computer and avionics systems.