Basic Electrical & Electronics Engineering
- What is the working principle of a DC motor and how does Fleming's left-hand rule apply? In one line A DC motor works because a current-carrying conductor placed in a magnetic field experiences a force F = BIl , and the commutato... 1
- What is back EMF in a DC motor and why is it important for the motor's operation? In one line Back EMF is the voltage generated in the rotating armature of a DC motor that opposes the supply voltage; it automatically contr... 1
- How does a three-phase supply create a rotating magnetic field in an induction motor stator? In one line When a balanced three-phase current flows in three stator windings placed 120° apart in space, the combined flux has constant ma... 1
- What are the main parts of a DC motor and what is the function of each part? In one line A DC motor consists of a stationary field system (yoke, poles, field winding) and a rotating armature (armature core, winding, c... 1
- How does a three-phase induction motor work, and what is slip? In one line The rotating stator field cuts the rotor conductors, induces currents in them, and the resulting force drags the rotor along in... 1
- What are the types of DC motors and where are shunt, series and compound motors used? In one line DC motors are classified by how the field winding is connected to the armature: separately excited and self-excited (shunt, seri... 1
- Where are BLDC motors used, and what are their advantages and limitations? In one line BLDC motors are used wherever high efficiency, long life, quiet operation and precise speed control matter, such as fans, electr... 1
- How is a three-phase induction motor constructed, and how do squirrel-cage and slip-ring rotors compare? In one line A three-phase induction motor has a stator with a distributed three-phase winding in a laminated slotted core, and a rotor that... 1
- Why is a single-phase induction motor not self-starting, according to double revolving field theory? In one line A single-phase winding produces a pulsating (not rotating) flux, which can be split into two equal fields rotating in opposite d... 1
- What are the types of single-phase induction motors and where is each type used? In one line Single-phase induction motors are named by how they create starting torque: split-phase, capacitor-start, capacitor-start capaci... 1
- What is a BLDC motor and how does electronic commutation replace brushes? In one line A brushless DC (BLDC) motor has permanent magnets on the rotor and windings on the stator, and an electronic controller switches... 1
- What is the structure of a bipolar junction transistor and why are its three regions doped differently? In one line A BJT is a three-layer semiconductor device (n-p-n or p-n-p) with an emitter, a base and a collector forming two p-n junctions;... 1
- What is the structure of a junction field effect transistor and how is it different from a BJT? In one line A JFET is a bar of n-type (or p-type) semiconductor forming a channel between source and drain, with heavily doped regions of th... 1
- How does an NPN transistor work in the active region, and what are alpha and beta? In one line In the active region, the forward-biased emitter-base junction injects electrons into the thin base, almost all of which are swe... 1
- What are the input and output characteristics of a BJT in common emitter configuration? In one line In common emitter (CE) configuration, the input characteristic is I_B versus V_BE at constant V_CE , and the output characterist... 1
- How does an n-channel JFET operate, and what are pinch-off and its drain characteristics? In one line In an n-channel JFET, a negative gate-source voltage widens the depletion regions and narrows the channel, reducing drain curren... 1
- How is an enhancement MOSFET built, and how does a gate voltage create a conducting channel? In one line An enhancement n-channel MOSFET has n^+ source and drain regions in a p-type substrate and a metal gate insulated by a thin oxid... 1
- How does a common emitter BJT amplifier amplify a small signal, and why is output inverted? In one line A CE amplifier is biased at a Q-point in the active region; a small AC input at the base varies the base current, which varies t... 1
- What is the transformation ratio of a transformer and how does it relate voltage, current and turns? In one line The transformation ratio K = N₂/N₁ = E₂/E₁ = I₁/I₂ tells how the transformer changes voltage and current: voltage scales with tu... 1
- How does a FET work as an amplifier in the common source configuration? In one line In a common-source FET amplifier, the FET is biased in its saturation (pinch-off) region; a small AC gate voltage varies the dra... 1
- What is an ideal transformer, and what assumptions make a transformer ideal? In one line An ideal transformer is an imaginary transformer with no losses, no leakage flux and zero magnetising current, so output power e... 1
- How do BJTs and MOSFETs work as electronic switches between cut-off and saturation? In one line A transistor works as a switch by being driven fully OFF (cut-off, like an open switch) or fully ON (saturation for a BJT, low-r... 1
- What happens inside a transformer when a load is connected to its secondary winding? In one line When load current flows in the secondary, its MMF tries to reduce the core flux, so the primary automatically draws an extra cur... 1
- How are transistors used in oscillators, and what is the Barkhausen criterion for oscillation? In one line An oscillator is an amplifier (BJT or FET) with positive feedback through a frequency-selective network; it produces a sustained... 1