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Question 1. Which law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points? A) Kirchhoff's Voltage Law B) Ohm's Law C) Faraday's Law D) Coulomb's Law Answer: B Explanation: Ohm's Law defines the relationship between voltage, current, and resistance, stating that current is directly proportional to voltage. Question 2. In a series circuit, the total resistance is: A) The sum of individual resistances B) The reciprocal of the sum of conductances C) Equal to the resistance of the largest resistor D) Zero if resistors are connected in parallel Answer: A
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Explanation: In series, resistances add directly, so the total resistance equals the sum of individual resistances. Question 3. Kirchhoff's Current Law (KCL) states that the algebraic sum of currents entering a junction is: A) Equal to the sum of currents leaving the junction B) Zero C) Equal to the voltage across the junction D) Equal to the total resistance at the junction Answer: B Explanation: KCL states that the total current entering a junction equals the total current leaving, implying the sum is zero when considering currents with appropriate signs. Question 4. Thevenin's Theorem is used to simplify a complex network to: A) A current source and a resistor in parallel B) A voltage source in series with a resistor C) A current source in parallel with a resistor D) A simplified resistor network only
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Answer: B Explanation: RMS (Root Mean Square) value for sinusoidal signals is the peak value divided by √2, representing the equivalent DC value. Question 7. The power factor of an AC circuit is the cosine of the: A) Frequency B) Phase difference between voltage and current C) Voltage across the load D) Resistance in the circuit Answer: B Explanation: Power factor is the cosine of the phase angle between voltage and current, indicating the efficiency of power transfer. Question 8. In a series R-L circuit, the impedance is: A) Purely resistive B) Purely inductive C) A combination of resistance and inductive reactance D) Zero at resonance Answer: C
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Explanation: Impedance in R-L circuits combines resistance and inductive reactance as a vector sum. Question 9. The magnetic field around a straight conductor carrying current: A) Is uniform and static B) Forms concentric circles around the conductor C) Is directed along the conductor's length D) Is negligible in practical applications Answer: B Explanation: Magnetic field lines around a current-carrying straight conductor are concentric circles. Question 10. Fleming's Left-Hand Rule is used to determine: A) The direction of induced EMF B) The direction of force on a current-carrying conductor in a magnetic field C) The polarity of a diode D) The phase relationship in AC circuits Answer: B
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Explanation: The energy stored in an inductor is 12LI2\frac{1}{2} L I^221 LI 2, representing magnetic energy. Question 13. The electric field in electrostatics is: A) A vector field that exerts force on charges B) A scalar quantity only C) Zero outside the charge distribution D) Always directed from negative to positive charges Answer: A Explanation: Electric field is a vector field that exerts force on charges, directed from positive to negative. Question 14. Capacitance is directly proportional to: A) The charge stored on the plates B) The voltage across the capacitor C) The area of the plates and the dielectric constant D) The resistance in the circuit Answer: C
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Explanation: Capacitance depends on the physical characteristics of the capacitor, such as plate area and dielectric constant. Question 15. In a RC charging circuit, the time constant is defined as: A) The time taken to charge the capacitor fully B) The product of resistance and capacitance (τ = RC) C) The inverse of the frequency of the AC source D) The duration of the voltage wave Answer: B Explanation: The time constant τ = RC characterizes the exponential charging/discharging of a capacitor. Question 16. A transformer operates on the principle of: A) Electromagnetic induction B) Mechanical rotation C) Thermal conduction D) Piezoelectric effect Answer: A
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Explanation: Slip measures how much the rotor lags behind the synchronous speed, essential for torque production. Question 19. Synchronous machines are used primarily for: A) Variable speed drives B) Power generation and voltage regulation C) Direct current conversion D) Small household appliances Answer: B Explanation: Synchronous machines are mainly used as generators for power production and for voltage regulation. Question 20. The power factor correction in a circuit is achieved by adding: A) Inductive reactance in series B) Capacitors in parallel C) Resistors in series D) Inductors in parallel Answer: B
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Explanation: Capacitors are used to improve power factor by compensating reactive power, usually connected in parallel. Question 21. The primary purpose of a fuse in an electrical circuit is to: A) Limit the current flow during overloads or faults B) Step down voltage levels C) Regulate power factor D) Convert AC to DC Answer: A Explanation: Fuses protect circuits by breaking the circuit when current exceeds a safe level, preventing damage. Question 22. Which device is used for measuring high voltages? A) Multimeter B) Voltmeter with high resistance C) Oscilloscope with a high-voltage probe D) Ammeter Answer: C
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Explanation: De Morgan's theorems provide rules for simplifying logical expressions involving negation. Question 25. The logical gate that outputs true only when both inputs are true is: A) AND gate B) OR gate C) NOT gate D) XOR gate Answer: A Explanation: AND gate outputs high only when all inputs are high. Question 26. In a three-phase induction motor, the rotating magnetic field is produced by: A) The stator windings supplied with three-phase AC B) The rotor conducting bars alone C) The rotor's slip frequency D) The permanent magnets in the rotor Answer: A
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Explanation: The stator receives three-phase AC, producing a rotating magnetic field essential for operation. Question 27. The primary purpose of a starter in an AC motor is to: A) Increase the starting torque and limit inrush current B) Connect the motor to the power supply permanently C) Reduce the motor's speed D) Control the power factor Answer: A Explanation: Starters limit the initial inrush current and provide higher starting torque. Question 28. The efficiency of an electrical generator is primarily affected by: A) Copper and iron losses B) The number of poles C) The type of winding used D) The frequency of the supply Answer: A
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Explanation: Fuses act as overcurrent protectors, melting when current exceeds rated value. Question 31. The unit of electric flux density is: A) Coulomb per square meter (C/m²) B) Volt per meter (V/m) C) Tesla (T) D) Weber (Wb) Answer: A Explanation: Electric flux density, also called electric displacement field, has units of Coulombs per square meter. Question 32. The relative permittivity of a dielectric material influences: A) The capacitance of a capacitor B) The resistance of a resistor C) The frequency response of a circuit D) The magnetic field strength Answer: A
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Explanation: Relative permittivity increases capacitance by allowing more charge storage. Question 33. The energy stored in a capacitor is: A) 12CV2\frac{1}{2} C V^221 CV 2 B) CVC V CV C) QVQ V QV D) LI2L I^2 LI 2 Answer: A Explanation: Stored energy in a capacitor is given by 12CV2\frac{1}{2} C V^221 CV 2. Question 34. The main purpose of the series resonance in an RLC circuit is to: A) Minimize impedance and maximize current B) Maximize impedance and minimize current C) Block AC signals D) Convert AC to DC Answer: A
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Explanation: In a balanced three-phase system, voltages are separated by 120° phase differences. Question 37. The purpose of a differential relay in a power system is to: A) Detect and isolate faults within a protected zone B) Control the power factor C) Regulate voltage at the generator terminal D) Synchronize generators Answer: A Explanation: Differential relays detect differences in current, signaling faults within the protected zone. Question 38. The primary reason for using step-up transformers in power transmission is to: A) Reduce transmission losses by increasing voltage B) Increase current to reduce conductor size C) Decrease the voltage for safety D) Convert AC to DC Answer: A
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Explanation: Increasing voltage reduces current for the same power, minimizing transmission line losses. Question 39. The maximum power transfer theorem states that maximum power is transferred when: A) The load resistance equals the source resistance (or Thevenin resistance) B) The load resistance is zero C) The source voltage is maximum D) The circuit is purely reactive Answer: A Explanation: Maximum power transfer occurs when the load resistance matches the source (or Thevenin) resistance. Question 40. In a control system, the feedback loop is used to: A) Stabilize the system and improve accuracy B) Increase the system's bandwidth C) Convert AC to DC D) Isolate the system from disturbances Answer: A
