Basic Electrical & Electronics Engineering
- How is transformer efficiency defined and at what condition is it maximum? In one line Transformer efficiency is output power divided by input power, and it is maximum at the load where variable copper loss equals c... 1
- How does a practical transformer differ from an ideal one, and what is its no-load current? In one line A practical transformer has winding resistance, leakage flux, core losses and finite permeability, so even at no load it draws a... 1
- What are iron losses and copper losses in a transformer and how are they reduced? In one line A transformer loses power as iron (core) loss, made of hysteresis and eddy-current losses that stay almost constant, and copper... 1
- How does a light emitting diode produce light, and what decides the colour of an LED? In one line An LED is a forward-biased p-n junction in which electrons recombine with holes and release their energy as photons; the colour... 1
- What are the main applications of single-phase transformers in power systems and electronics? In one line Single-phase transformers are used wherever AC voltage must be stepped up, stepped down, isolated or matched, from power distrib... 1
- What is the internal structure of an LED and why does it need a series resistor? In one line An LED is a p-n junction chip with a thin top layer for light to escape, mounted in a reflector cup inside a transparent epoxy l... 1
- How are LEDs used in indicator lamps and seven-segment and dot-matrix displays? In one line LEDs are used as indicator lamps to show the status of a device and are arranged as segments or dot grids to display digits, let... 1
- What is a Zener diode, and how do Zener breakdown and avalanche breakdown differ? In one line A Zener diode is a heavily doped silicon p-n junction diode designed to work safely in reverse breakdown, where its voltage stay... 1
- What does the V-I characteristic of a Zener diode look like and what do its key points mean? In one line The Zener V-I characteristic is like a normal diode in forward bias, but in reverse bias the current stays almost zero until V_Z... 1
- How does a Zener diode work as a voltage regulator against changes in input and load? In one line In a Zener shunt regulator, a series resistor drops the extra input voltage while the Zener diode, connected in reverse across t... 1
- How are LEDs used for lighting, and why are they replacing incandescent and CFL lamps? In one line White LEDs, usually a blue LED chip coated with yellow phosphor, are used in bulbs, tubes, street lights, vehicles and display b... 1
- How is a sinusoidal alternating voltage generated by a coil rotating in a magnetic field? In one line When a coil rotates at constant speed in a uniform magnetic field, the flux linking it changes continuously, so by Faraday's law... 1
- What do cycle, time period, frequency, amplitude and instantaneous value mean for an AC wave? In one line These are the basic terms that describe a repeating AC waveform: how big it gets (amplitude), how long one repetition takes (tim... 1
- What is the RMS value of an alternating current and why is it 0.707 times the peak? In one line The RMS (root mean square) value of an alternating current is the steady DC current that would produce the same heat in a resist... 1
- What is the average value of a sine wave, and how are form factor and peak factor defined? In one line The average value of a sine wave over a half cycle is 2V_m/π ≈ 0.637V_m ; form factor is RMS ÷ average (1.11) and peak factor is... 1
- What is a phasor, and how do you find phase difference between two AC quantities? In one line A phasor is a rotating line whose length represents the RMS (or peak) value of a sinusoid and whose angle represents its phase,... 1
- How do you add or subtract sinusoidal AC quantities using phasors and complex numbers? In one line To add or subtract sinusoids of the same frequency, write each as a phasor in rectangular form (a + jb) , add or subtract the re... 1
- How do current and voltage behave in purely resistive, inductive and capacitive AC circuits? In one line In a pure resistor current is in phase with voltage, in a pure inductor current lags voltage by 90°, and in a pure capacitor cur... 1
- How do you analyse a series RL circuit: impedance, phase angle and power factor? In one line In a series RL circuit the impedance is Z = √(R² + X_L²) , the current lags the voltage by φ = tan⁻¹(X_L/R) , and the power fact... 1
- How do you analyse a series RC circuit and why does its current lead the voltage? In one line In a series RC circuit the impedance is Z = √(R² + X_C²) and the current leads the supply voltage by φ = tan⁻¹(X_C/R) , giving a... 1
- How do you analyse a series RLC circuit and decide if it is inductive or capacitive? In one line In a series RLC circuit Z = √(R² + (X_L - X_C)²) ; if X_L > X_C it behaves inductively (current lags), if X_C > X_L capacitively... 1
- What is admittance, and how is it used to solve parallel AC circuits? In one line Admittance Y = 1/Z measures how easily a branch allows AC to flow; in a parallel circuit, branch admittances simply add, making... 1
- What are real power, reactive power, apparent power and power factor in an AC circuit? In one line Real power P = VIcosφ (W) does useful work, reactive power Q = VIsinφ (VAR) flows back and forth to build magnetic and electric... 1
- What is series resonance in an RLC circuit and what is its resonant frequency? In one line Series resonance occurs at the frequency where X_L = X_C , so the impedance becomes purely resistive and minimum, the current is... 1