Free Practice Questions for Engineer Electric Work

Electrical Applications & Construction Materials (전기응용 및 공사재료)

Illumination engineering (luminous intensity, illuminance, luminance, room index, maintenance and utilization factors, indoor lighting calculation formula N = EA/FUM, LED and HID characteristics, color rendering), electric heating (resistance heating, induction heating skin depth δ = √(ρ/(π·f·μ)), dielectric heating P = 2π·f·C·V²·tanδ, arc furnaces, thermal power and efficiency), electric traction (train resistance, tractive effort, speed-time curve, traction motor characteristics, regenerative braking), electrochemistry (Faraday's laws of electrolysis, secondary battery chemistry: lead-acid and lithium-ion, state of health SOH, charging methods: CC-CV, float/trickle charge), and electrical construction materials (copper vs aluminum conductivity, XLPE/PVC insulation, rigid steel and flexible conduit, cable trays, wireways, busways, high-voltage insulators, knife switches, MCCB, and HRC fuses).

Power Engineering (전력공학)

Transmission line parameters (conductor resistance, line inductance with GMD/GMR calculations, line capacitance, bundle conductor benefits), line performance (short-line lumped modeling, medium-line nominal T and π networks, long-line distributed parameters and hyperbolic functions, characteristic surge impedance Z0, Ferranti effect at no-load, percentage voltage regulation), power distribution systems (radial vs loop distribution, load factor, diversity factor > 1, loss factor, three-phase line voltage drop e = √3·I(R cosθ + X sinθ)), fault analysis (per-unit system base conversions, symmetrical components: positive, negative, and zero sequence transformations, 3-phase symmetrical short-circuit current and MVA, single line-to-ground fault If = 3·I0), and system protection (overcurrent relays OCR, ground fault OCGR, directional distance relays, differential relays 87, circuit breaker interrupting capacity VCB/GCB/ACB, metal oxide ZnO lightning arresters, and BIL insulation coordination).

Electrical Machinery (전기기기)

DC machines (shunt, series, and compound generators and motors; torque T = k·Φ·Ia, speed equations, armature reaction demagnetizing and cross-magnetizing effects, commutating poles, speed control methods, starting rheostats), transformers (equivalent circuit parameters referred to windings, voltage regulation formula, core iron losses vs copper losses, maximum efficiency condition Pi = m²Pc, open-circuit and short-circuit tests, three-phase transformer connections: Y-Y, Δ-Δ, Y-Δ, V-V open-delta capacity Pv = √3·P1, parallel operation conditions), induction motors (revolving magnetic field, synchronous speed Ns = 120f/p, slip s, rotor frequency, equivalent circuit, torque-slip curve, maximum breakdown torque independent of rotor resistance, proportional shift, squirrel-cage starting methods: DOL, star-delta, auto-transformer; inverter V/f control), synchronous machines (synchronous generators: armature reaction at unity, lagging, and leading power factors, synchronous impedance Zs, short-circuit ratio SCR, voltage regulation; synchronous motors: V-curves, synchronous condenser power factor correction, damper windings), and power converters (diodes, thyristors SCR, firing angle delay, IGBT, half-wave/full-wave and three-phase bridge rectifiers, and PWM inverters).

Circuit Theory & Control Engineering (회로이론 및 제어공학)

Circuit theorems (Ohm's law, KVL, KCL, Thevenin and Norton equivalent networks, maximum power transfer theorem, complex impedance Z and admittance Y, series and parallel RLC resonance, quality factor Q, bandwidth BW = f0/Q), three-phase balanced circuits (star and delta connections, phase vs line relationships, total three-phase active power P = √3·VL·IL·cosθ, reactive power, two-wattmeter method P = W1 + W2, Q = √3(W1 - W2)), transient response (first-order RL and RC time constants τ = L/R and τ = RC, RLC transient damping: overdamped, critically damped, underdamped), two-port networks (Z, Y, h, and ABCD transmission parameters, reciprocity AD - BC = 1, cascade matrix multiplication), control systems fundamentals (open-loop and closed-loop transfer functions, block diagram reduction, Mason's gain formula for signal flow graphs), time-domain response (standard second-order system transfer function G(s) = ωn²/(s² + 2ζωn·s + ωn²), damping ratio ζ, natural frequency ωn, overshoot, settling time, steady-state error and system types), and stability analysis (Routh-Hurwitz stability criterion, root locus rules and asymptotes, Nyquist stability criterion, Bode plots, gain and phase margins).

Technical Standards for Electrical Facilities (전기설비기술기준 / KEC)

Korea Electrotechnical Code (KEC) statutory framework and voltage classifications (low voltage AC ≤ 1 kV, DC ≤ 1.5 kV; high voltage; extra-high voltage > 7 kV), earthing systems (TN-S, TN-C, TN-C-S, TT, IT system architectures; protective conductor PE sizing rules, main and supplementary equipotential bonding), overcurrent protection and conductor sizing (current-carrying capacity Iz, device rating In, design current Ib, coordination rules Ib ≤ In ≤ Iz and I2 ≤ 1.45·Iz), protection against electric shock (automatic disconnection of supply ADS, high-sensitivity RCD rated residual current IΔn ≤ 30 mA and operating time ≤ 0.03 s for personnel safety, SELV and PELV requirements), low-voltage indoor wiring methods (rigid metallic conduit, synthetic resin conduit thickness and support spacing, cable trays and ladder fill ratios, metal wireways, bus ducts, underground direct burial depths ≥ 1.0 m under roadways / ≥ 0.75 m elsewhere), outdoor overhead lines (ground clearances over roadways, railways, pedestrian paths, wind pressure load categories Gap/Eul/Byeong, support safety factors), substation and transformer installations (fire-separation barriers, 100% oil containment catch basins), and renewable energy and special installations (photovoltaic PV DC arc protection and disconnect switches, energy storage systems ESS safety and indoor SOC limits ≤ 80%, EV charging facility protection and Type B / Type A+6mA RCD requirements).