Electronic workshop Dr. Imtiaz Hussain URL : Lecture-5 Inductors and Transformers

Inductors Generally - coil of conducting wire – Usually wrapped around a solid core. If no core is used, then the inductor is said to have an ‘air core’.

Symbols

4 Inductors Values specified in henries (H), millihenries (mH) and microhenries (μH). Inductor can be fixed value or variable. Fixed Value Inductor Variable Inductor

5 Inductor types Molded inductor & air-wound inductorAdjustable air-wound inductor Ferrite core toroidal transformerIron powder toroidal inductorAir wound inductor

6 Inductor ratings Wire gauge and physical size of the coil determine the current handling capacity. Core material will have a temperature dependence. Air is best, followed by iron powder, then ferrites.

7 Inductor handling Inductors are not polarized and may be installed in either direction. Mechanical stress due to lead bending should be minimized. Inductors in timing or frequency determining circuits should be installed in a mechanically rigid fashion.

Color Coding

Inductor Applications Speakers Solenoid Valves Resonant Circuits

Task#1 An ideal inductor would exhibit zero resistance but a real inductor has some finite resistance. Inductors which have become open will show infinite resistance, whereas shorted inductors will show a resistance of zero Ohms. Take few resistors and check them for any faults.

Transformers A transformer is a device that uses a pair of coils/windings to manipulate AC voltage and current. It uses the principle of mutual induction to either decrease or increase the voltage/current at its input.

Transformers

The voltage/current at the output of the transformer is given by the following equation:

Task#2 S N.o Peak to Peak Input Voltage Output VoltageTurn Ratio

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