Title: Electrical Engineering Fundamentals — LearnCoachAssist

Q: What is Ohm's law?
A: Ohm's law states that V = IR, where V is voltage (volts), I is current (amps), and R is resistance (ohms).

Q: How do you calculate current using Ohm's law?
A: I = V / R. Current equals voltage divided by resistance.

Q: How do you calculate resistance using Ohm's law?
A: R = V / I. Resistance equals voltage divided by current.

Q: What is the unit of electrical resistance?
A: The ohm (Ω), named after Georg Simon Ohm.

Q: What is electrical power in terms of voltage and current?
A: P = VI, where P is power in watts, V is voltage, and I is current.

Q: Express electrical power using Ohm's law substitutions.
A: P = I²R or P = V²/R, derived by substituting Ohm's law into P = VI.

Q: What is Kirchhoff's Current Law (KCL)?
A: The sum of all currents entering a node equals the sum of all currents leaving that node: ΣI_in = ΣI_out.

Q: What is Kirchhoff's Voltage Law (KVL)?
A: The sum of all voltage drops around any closed loop in a circuit equals zero: ΣV = 0.

Q: What principle does KCL rely on?
A: Conservation of charge — charge cannot accumulate at a node in a circuit.

Q: What principle does KVL rely on?
A: Conservation of energy — the total energy gained equals the total energy lost around a closed loop.

Q: What is the difference between DC and AC current?
A: DC (direct current) flows in one constant direction; AC (alternating current) periodically reverses direction.

Q: What is the standard household AC frequency in the United States?
A: 60 Hz. The voltage alternates at 60 cycles per second.

Q: What is the standard household AC frequency in Europe?
A: 50 Hz. The voltage alternates at 50 cycles per second.

Q: What is the RMS value of an AC sine wave?
A: V_rms = V_peak / √2 ≈ 0.707 × V_peak. It represents the equivalent DC voltage for power delivery.

Q: What is the peak voltage of a 120V RMS AC supply?
A: V_peak = 120 × √2 ≈ 169.7 V.

Q: How are resistors combined in series?
A: R_total = R₁ + R₂ + R₃ + …. Resistances add directly in series.

Q: How are resistors combined in parallel?
A: 1/R_total = 1/R₁ + 1/R₂ + 1/R₃ + …. The reciprocals of resistances add.

Q: What is a voltage divider?
A: A circuit where V_out = V_in × R₂ / (R₁ + R₂), used to produce a fraction of the input voltage.

Q: What is a capacitor?
A: A passive component that stores energy in an electric field between two conductive plates separated by a dielectric.

Q: What is the unit of capacitance?
A: The farad (F), defined as one coulomb per volt.

Q: What is the relationship between charge, capacitance, and voltage?
A: Q = CV, where Q is charge in coulombs, C is capacitance, and V is voltage.

Q: What is the energy stored in a capacitor?
A: E = ½CV², where C is capacitance and V is voltage across the capacitor.

Q: How does a capacitor behave in a DC steady-state circuit?
A: It acts as an open circuit — no current flows once the capacitor is fully charged.

Q: How are capacitors combined in parallel?
A: C_total = C₁ + C₂ + C₃ + …. Capacitances add directly in parallel.

Q: How are capacitors combined in series?
A: 1/C_total = 1/C₁ + 1/C₂ + 1/C₃ + …. The reciprocals of capacitances add.

Q: What is the impedance of a capacitor at frequency ω?
A: Z_C = 1 / (jωC), where j is the imaginary unit and ω is angular frequency.

Q: What is an inductor?
A: A passive component that stores energy in a magnetic field, typically a coil of wire.

Q: What is the unit of inductance?
A: The henry (H), defined as one volt-second per ampere.

Q: What is the energy stored in an inductor?
A: E = ½LI², where L is inductance and I is current through the inductor.

Q: How does an inductor behave in a DC steady-state circuit?
A: It acts as a short circuit — it passes DC current with zero impedance once current is stable.

Q: What is the impedance of an inductor at frequency ω?
A: Z_L = jωL, where j is the imaginary unit and ω is angular frequency.

Q: How are inductors combined in series?
A: L_total = L₁ + L₂ + L₃ + …. Inductances add directly in series (assuming no mutual coupling).

Q: How are inductors combined in parallel?
A: 1/L_total = 1/L₁ + 1/L₂ + 1/L₃ + …. The reciprocals of inductances add.

Q: What is the time constant of an RC circuit?
A: τ = RC, measured in seconds. It is the time for voltage to reach ~63.2% of its final value.

Q: What is the time constant of an RL circuit?
A: τ = L/R, measured in seconds. It is the time for current to reach ~63.2% of its final value.

Q: What is the resonant frequency of an LC circuit?
A: f₀ = 1 / (2π√(LC)). At this frequency, inductive and capacitive reactances cancel.

Q: What is a transistor?
A: A semiconductor device used to amplify or switch electronic signals and electrical power.

Q: What are the two main types of transistors?
A: BJT (Bipolar Junction Transistor) and MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

Q: What are the three terminals of a BJT?
A: Base, Collector, and Emitter.

Q: What are the three terminals of a MOSFET?
A: Gate, Drain, and Source.

Q: What are the two types of BJT?
A: NPN and PNP. NPN is controlled by positive base current; PNP by negative.

Q: What is the current gain (β) of a BJT?
A: β = I_C / I_B, the ratio of collector current to base current. Typical values range from 50 to 300.

Q: How does a MOSFET differ from a BJT in control mechanism?
A: A MOSFET is voltage-controlled (gate voltage), while a BJT is current-controlled (base current).

Q: What are the three operating regions of a MOSFET?
A: Cutoff (off), Triode/Linear (resistive), and Saturation (constant current/amplification).

Q: What is the threshold voltage (V_th) of a MOSFET?
A: The minimum gate-to-source voltage required to create a conducting channel between drain and source.

Q: What is an operational amplifier (op-amp)?
A: A high-gain differential voltage amplifier with inverting (−) and non-inverting (+) inputs and a single output.

Q: What are the two golden rules of an ideal op-amp with negative feedback?
A: 1) No current flows into the inputs (infinite input impedance). 2) The voltage difference between inputs is zero (V+ = V−).

Q: What is the gain of an inverting op-amp configuration?
A: A_v = −R_f / R_in, where R_f is the feedback resistor and R_in is the input resistor.

Q: What is the gain of a non-inverting op-amp configuration?
A: A_v = 1 + R_f / R_in, where R_f is the feedback resistor and R_in is the ground-connected resistor.

Q: What is a voltage follower (buffer) op-amp circuit?
A: An op-amp with output connected directly to the inverting input; gain = 1, providing impedance matching.

Q: What is the gain-bandwidth product (GBP) of an op-amp?
A: A constant equal to open-loop gain × bandwidth. As gain increases, bandwidth decreases proportionally.

Q: What is a summing amplifier?
A: An inverting op-amp circuit that outputs the weighted sum of multiple input voltages: V_out = −R_f(V₁/R₁ + V₂/R₂ + …).

Q: What is a comparator?
A: An op-amp used without feedback that outputs high or low depending on which input is greater.

Q: What does an AND gate do?
A: Outputs 1 only when all inputs are 1. Boolean expression: Y = A · B.

Q: What does an OR gate do?
A: Outputs 1 when at least one input is 1. Boolean expression: Y = A + B.

Q: What does a NOT gate (inverter) do?
A: Outputs the complement of the input. Boolean expression: Y = Ā.

Q: What does a NAND gate do?
A: Outputs 0 only when all inputs are 1. It is the complement of AND: Y = (A · B)̄.

Q: What does a NOR gate do?
A: Outputs 1 only when all inputs are 0. It is the complement of OR: Y = (A + B)̄.

Q: What does an XOR gate do?
A: Outputs 1 when inputs are different. Boolean expression: Y = A ⊕ B.

Q: Why is the NAND gate called a universal gate?
A: Any Boolean function can be implemented using only NAND gates, including AND, OR, and NOT.

Q: What is De Morgan's first theorem?
A: (A · B)̄ = Ā + B̄. The complement of a product equals the sum of the complements.

Q: What is De Morgan's second theorem?
A: (A + B)̄ = Ā · B̄. The complement of a sum equals the product of the complements.

Q: What is a flip-flop in digital electronics?
A: A bistable circuit that stores one bit of data, toggling between two stable states (0 or 1).

Q: What is the difference between a latch and a flip-flop?
A: A latch is level-triggered (responds while clock is high/low); a flip-flop is edge-triggered (responds on clock transitions).

Q: What is a multiplexer (MUX)?
A: A combinational circuit that selects one of many inputs and forwards it to a single output based on select lines.

Q: What is the purpose of an ADC?
A: An Analog-to-Digital Converter transforms continuous analog signals into discrete digital values.

Q: What is the purpose of a DAC?
A: A Digital-to-Analog Converter transforms discrete digital values into continuous analog signals.

Q: What is three-phase power?
A: A system using three AC voltages offset by 120°, providing constant power delivery and efficient transmission.

Q: What is the advantage of three-phase over single-phase power?
A: Three-phase delivers more power with less conductor material and produces a constant (non-pulsating) power output.

Q: What is a transformer?
A: A device that transfers AC electrical energy between circuits via electromagnetic induction, changing voltage levels.

Q: What is the transformer voltage ratio equation?
A: V₁/V₂ = N₁/N₂, where N is the number of turns. More secondary turns means higher output voltage.

Q: What is the power factor?
A: PF = cos(θ), the ratio of real power to apparent power. A PF of 1 means all power is useful.

Q: What is real (active) power?
A: Power actually consumed by the load, measured in watts (W): P = VI cos(θ).

Q: What is reactive power?
A: Power stored and released by inductors/capacitors, measured in volt-amperes reactive (VAR): Q = VI sin(θ).

Q: What is apparent power?
A: The product of RMS voltage and current: S = VI, measured in volt-amperes (VA). Related by S² = P² + Q².

Q: Why is power factor correction important?
A: Low power factor increases current draw and transmission losses. Correction (often via capacitors) reduces wasted energy.

Q: What is the Nyquist sampling theorem?
A: A signal must be sampled at at least twice its highest frequency (2f_max) to be accurately reconstructed.

Q: What is aliasing in signal processing?
A: Distortion that occurs when a signal is sampled below the Nyquist rate, causing high frequencies to appear as lower frequencies.

Q: What is a Fourier Transform?
A: A mathematical tool that decomposes a signal into its constituent sinusoidal frequencies (frequency-domain representation).

Q: What is the difference between DFT and FFT?
A: The FFT is an efficient algorithm to compute the DFT (Discrete Fourier Transform), reducing complexity from O(N²) to O(N log N).

Q: What is a low-pass filter?
A: A filter that passes frequencies below a cutoff frequency and attenuates higher frequencies.

Q: What is a high-pass filter?
A: A filter that passes frequencies above a cutoff frequency and attenuates lower frequencies.

Q: What is the cutoff frequency of a simple RC low-pass filter?
A: f_c = 1 / (2πRC). At this frequency the output is −3 dB (≈70.7%) of the input.

Q: What is a band-pass filter?
A: A filter that passes frequencies within a specific range and attenuates frequencies outside that range.

Q: What does −3 dB mean in filter design?
A: It is the half-power point where output power is half the input power, and voltage is ≈70.7% of maximum.

Q: What is Coulomb's law?
A: The force between two point charges: F = kq₁q₂/r², where k ≈ 8.99 × 10⁹ N·m²/C².

Q: What is Gauss's law?
A: The total electric flux through a closed surface equals the enclosed charge divided by ε₀: ∮E·dA = Q_enc/ε₀.

Q: What is Faraday's law of electromagnetic induction?
A: A changing magnetic flux through a loop induces an EMF: ε = −dΦ_B/dt. The negative sign reflects Lenz's law.

Q: What is Lenz's law?
A: The direction of an induced current is such that it opposes the change in magnetic flux that produced it.

Q: What is Ampère's law (with Maxwell's correction)?
A: ∮B·dl = μ₀(I_enc + ε₀ dΦ_E/dt). Relates magnetic field around a loop to current and changing electric flux.

Q: What are Maxwell's four equations?
A: Gauss's law (E), Gauss's law (B) (no magnetic monopoles), Faraday's law, and Ampère-Maxwell law.

Q: What is the speed of electromagnetic waves in vacuum?
A: c = 1/√(μ₀ε₀) ≈ 3 × 10⁸ m/s, derived from Maxwell's equations.

Q: What is impedance?
A: The total opposition to AC current flow, combining resistance and reactance: Z = R + jX, measured in ohms.

Q: What is the quality factor (Q) of a resonant circuit?
A: Q = f₀ / Δf (center frequency / bandwidth). Higher Q means a sharper, more selective resonance peak.

Q: What is a Thevenin equivalent circuit?
A: Any linear circuit can be replaced by a single voltage source V_th in series with a resistance R_th.

Q: What is a Norton equivalent circuit?
A: Any linear circuit can be replaced by a single current source I_N in parallel with a resistance R_N.

Q: What is the relationship between Thevenin and Norton equivalents?
A: V_th = I_N × R_N and R_th = R_N. They are interconvertible.

Q: What is the superposition theorem?
A: In a linear circuit with multiple sources, the response is the algebraic sum of responses caused by each source acting alone.

Q: What is the maximum power transfer theorem?
A: Maximum power is delivered to a load when R_load = R_source (or Z_load = Z_source* for AC circuits).

Q: What is a Wheatstone bridge?
A: A circuit of four resistors used to precisely measure unknown resistance: balanced when R₁/R₂ = R₃/R₄.