Author: John Mulindi
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The Basics of Semiconductor Physics as the Foundation of Electronics
Metals have a large number of weakly bound electrons in what is called their conduction band. When an electric field is applied to a metal such as copper, the electrons migrate freely producing a current through the metal. Because of the ease by which large currents can flow in metals, they are called conductors. In…
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Basic Electronics – Multiple Choice Questions & Answers (MCQ1)
The Answers to these questions have been provided towards the end: Q1. A Transistor is a? A. Current controlled voltage device B. Current controlled current device C. Voltage controlled current device D. Voltage controlled voltage device Q2. The breakdown mechanism in a lightly doped p-n junction under reverse biased condition is called? A. Zener breakdown…
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Speed Control of a DC Compound Motor
A compound motor is a combination of a series and a shunt-wound motor. The Speed-torque characteristics for a compound motor Speed Control of a DC Compound Motor Speed is controlled by variable resistors in the shunt field and armature circuit. The series winding may be arranged that it aids the shunt field (cumulative compound) or…
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DC Shunt Motor Speed Control
In the shunt motor, the motor winding is in parallel with the armature. From the figure above, the supply current I = Ia + If . Unlike a series motor, if the load is removed from the motor, only the armature current will decrease, the field remaining at the same strength. Therefore the motor will…
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Speed Control of a DC Series Motor
The dc series motor has its windings and armature connected in series across the supply. From the figure above, the armature current Ia also supplies the field, hence when Ia is large on starting for example, the magnetic field will be strong, and the torque will be high. As the machine accelerates, the torque, armature…
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The Essential Components of An Electric Drive
Power electronics deals with the applications of solid-state electronics for the control and conversion of electric power. The conversion techniques require switching power semiconductor devices ON and OFF. The block diagram below shows the essential components of an electric drive controlled by a power semiconductor converter. The converter regulates the flow of power from the…
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Key Instruments Used By Electronics Engineers
Multimeter This is also called volt-ohm-milliammeter (VOM). It is a general purpose instrument having the circuitry and switching arrangement for measuring ac/dc voltage or ac/dc current or resistance. It is simple, compact and portable instrument because the only power it uses is the battery for the ohm-meter. Multimeters can be analog or digital type. Multimeters…
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Key Facts about Thyristor DC Motor Drives Operation
For motors up to a few kilowatts the armature converter draws power from either a single phase or 3-phase utility supply. For large motors, 3-phase power supply is preferred because the waveforms are much smoother although traction uses single-phase with a series inductor to smooth the current. A separate thyristor or diode rectifier is used…
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Step by Step Guide: How to Check and Test a Power Transformer
Testing of power transformers is continuous monitoring of faults in all units of such equipment and their timely removal after detection. All this is achieved with one objective continuation of the continuous activity of a significant node in the power supply system of many energy consumers. A variety of tests are used to determine the…
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The Basics Facts about Photons
Photons are the elemental units of electromagnetic spectrum. For example, white light is composed of a number of different kinds of photons, some are red photons, some are blue photons, etc. Note that, there is no white photon; instead the combination of the various colored photons when they interact with your eyes, your brain perceives…