ECN CHAPTER 1 electronics and telecommunications engineering lecture notes

Lecture notes of electric Circuits

1. PRAVIN PATIL COLLEGE OF DIPLOMA ENGG. & TECHNOLOGY BASIC ELECTRONIC COMPONENTS AND SIGNALS

2. The light-emitting diode (LED) When the device is forward-biased, electrons cross the pn junction from the n -type material and recombine with holes in the p -type material Since the electrons in the conduction band are at a higher energy level than the holes in the valence band, when recombination takes place, energy is released in the form of heat and light A large exposed surface on one layer of the LED permits the photons to be emitted as light, termed electroluminescence Light Emitting Diodes

3. LED

4. Symbol for an LED

5. Inductance - Self Inductance and Mutual Inductance We are aware that whenever an electric current flows through a conductor, a magnetic field surrounding it is produced. A varying current results in a varying magnetic field . Due to this, the magnetic flux varies and an electromotive force is induced in the circuit. 

6. What is Inductance? Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. L is used to represent the inductance, and Henry is the  SI unit of inductance . inductance is defined as the ratio of the induced voltage to the rate of change of current causing it.

7. Factors Affecting Inductance Number of Wire Turns in the Coil Inductance is greater when the number of turns of wire in the coil is greater. More coils of wires indicate a greater amount of magnetic field force for a given amount of coil current. Coil Area Inductance is proportional to the coil area. Greater the coil area, the greater the inductance. Greater coil area presents less opposition to the formation of magnetic field flux for a given amount of field force Core Material The greater the magnetic permeability of the core to which the coil is wrapped around, the greater the inductance. Coil Length The longer the coil’s length, the lesser the inductance. The shorter the coil’s length, the greater the inductance.

8. Types of Inductance Inductance is classified into two types as : Self Inductance Mutual Inductance

9. Self Inductance

10. Mutual Inductance When there is a change in the current or   magnetic flux   linked with the two coils, an opposing electromotive force is produced across each coil, and this phenomenon is termed Mutual Inductance.

11. Coefficient of coupling

12. Dot Convention

13. Coupling of Aiding type Consider the following electric circuit, which is having two inductors that are connected in  series . Since the two inductors are connected in series, the  same current  I  flow through both inductors having self-inductances L 1  and L 2 . In this case, the current, I enter at the dotted terminal of each inductor. Hence, the induced voltage in each inductor will be having  positive polarity  at the dotted terminal due to the current flowing in another coil.

14. Therefore, the  equivalent inductance  of series combination of inductors shown in the above figure is LEq =L1+L2+2MLEq=L1+L2+2M In this case, the equivalent inductance has been increased by 2M. Hence, the above electrical circuit is an example of  electrical  coupling which is of  aiding  type.

15. Coupling of Opposing type Consider the following electric circuit, which is having two inductors that are connected in  series . In the above circuit, the current  I  enters at the dotted terminal of the inductor having an inductance of  L 1 the current  I  leaves from the dotted terminal of the inductor having an inductance of  L 2 . Hence, it induces a voltage in the other inductor having an inductance of  L 1 . So,  negative polarity  of the induced voltage is present at the dotted terminal of this inductor.

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