BEE One Marks Questions PDF

J.B. INSTITUTE OF ENGINEERING & TECHNOLOGY (UGC AUTONOMOUS) Approved by AICTE, Accredited by NBA (CSE, ECE, EEE, IT) & NAAC and Permanently Affiliated to JNTUH Yenkapally (V), Moinabad (M), R.R District, Hyderabad – 500 075...

J.B. INSTITUTE OF ENGINEERING & TECHNOLOGY (UGC AUTONOMOUS) Approved by AICTE, Accredited by NBA (CSE, ECE, EEE, IT) & NAAC and Permanently Affiliated to JNTUH Yenkapally (V), Moinabad (M), R.R District, Hyderabad – 500 075 Ph.: 08413-235127, 235053; Fax: 08413-235753 E-mail: [email protected]; Website: www.jbiet.edu.in BASIC ELECTRICAL ENGINEERING: ONE-MARK QUESTIONS UNIT 1: DC CIRCUITS AND CIRCUIT ELEMENTS 1. Define voltage. Answer: Voltage is the electric potential difference between two points, which drives the flow of electric current in a circuit. 2. What is the unit of voltage? Answer: volts (v). 3. Define current. Answer: Current is the flow of electric charge through a conductor or circuit. 4. What is the unit of current? Answer: Ampere (A). 5. Define power. Answer: Rate of doing work or converting energy. 6. What is the unit of power? Answer: Watt (W). 7. Define energy. Answer: Capacity to do work. 8. What is the unit of energy? Answer: Joule (J). 9. Define open circuit. Answer: A circuit with no current flow due to a break. 10. Define short circuit. Answer: An unintended path with low resistance causing excessive current. 11. What is an active element? Answer: A component that can supply energy. 12. What is a passive element? Answer: A component that consumes energy. 13. Name a voltage source. Answer: Battery. 14. What is source conversion? Answer: Changing a voltage source to an equivalent current source and vice versa. 15. What is Ohm’s Law? Answer: V = IR. 16. State Kirchhoff's Current Law (KCL). Answer: The sum of currents entering a node equals the sum leaving it. 17. State Kirchhoff's Voltage Law (KVL). Answer: The sum of voltages in a closed loop equals zero. 18. What is the loop current method? Answer: A technique to solve circuit equations by considering closed loops. 19. Define resistance. Answer: Opposition to current flow. 20. What is the SI unit of resistance? Answer: Ohm (Ω). 21. What is the temperature coefficient of resistance? Answer: The rate of change of resistance with temperature. 22. What happens to resistance in series? Answer: Adds up (R = R1 + R2 +...). 23. What happens to resistance in parallel? Answer: Inverse adds (1/R = 1/R1 + 1/R2 +...). 24. What are the applications of a resistor? Answer: Current limiting, voltage division, heating element. 25. What is the energy-storing element in an inductor? Answer: Magnetic field. 26. What is the energy-storing element in a capacitor? Answer: Electric field. 27. Define inductance. Answer: Inductance is the property of a coil or circuit that opposes changes in current flow by generating an electromotive force (EMF). 28. What is the unit of inductance? Answer: Henry (H). 29. What is the unit of capacitance? Answer: Farad (F). 30. Define capacitance. Answer: The ability to store charge. 31. What is the VI relation for an inductor? Answer: V = L dI/dt. 32. What is the VI relation for a capacitor? Answer: I = C dV/dt. 33. What is the energy stored in an inductor? Answer: 1/2 L I^2. 34. What is the energy stored in a capacitor? Answer: 1/2 C V^2. 35. What happens to inductance in series? Answer: Adds up (L = L1 + L2 +...). 36. What happens to capacitance in parallel? Answer: Adds up (C = C1 + C2 +...). 37. What is the use of resistors? Answer: To limit current and divide voltage. 38. Name a practical application of capacitors. Answer: Filtering in power supplies. 39. Name a practical application of inductors. Answer: Energy storage in DC-DC converters. UNIT 2: AC CIRCUITS 1. Define alternating quantity. Answer: A value that changes periodically. 2. What is one cycle? Answer: A complete waveform of AC. 3. Define time period. Answer: Time for one complete cycle. 4. What is frequency? Answer: Number of cycles per second. 5. What is amplitude? Answer: Maximum value of a waveform. 6. What is the RMS value? Answer: Effective value of AC. 7. What is the average value of AC? Answer: The average of all instantaneous values over one cycle. 8. What is the form factor? Answer: Form Factor = RMS Value / Average Value. 9. What is the peak factor? Answer: Peak Factor = Peak Value / RMS Value. 10. Define phase. Answer: Angular position of a waveform. 11. What is phase difference? Answer: Angle by which one waveform leads or lags another. 12. What is the impedance of an RLC circuit? Answer: Z = √(R^2 + (XL - XC)^2). 13. Define resonance. Answer: A condition where XL = XC. 14. What is the resonance frequency? Answer: The frequency at which resonance occurs, f = 1/(2π√(LC)). 15. What happens at resonance in RLC? Answer: Maximum current flows. 16. Define phase sequence. Answer: The order in which phases reach their maximum. 17. What is a star connection? Answer: A three-phase connection where ends meet at a common point. 18. What is a delta connection? Answer: In a delta connection, the starting point of one winding is connected to the endpoint of the adjacent winding, forming a closed-loop. 19. Relation between line and phase voltage in star connection? Answer: VL = √3 VP. 20. Relation between line and phase current in delta connection? Answer: IL = √3 IP. 21. What is power factor? Answer: Ratio of real power to apparent power. 22. What is apparent power? Answer: Product of RMS voltage and current. 23. What is real power? Answer: Power consumed in a circuit (P = VIcosφ). 24. What is reactive power? Answer: Power stored in reactive elements (Q = VIsinφ). 25. What is balanced load? Answer: Equal impedance in all three phases. 26. What is unbalanced load? Answer: Unequal impedance in the phases. 27. What is a neutral wire? Answer: A return path for current in a star system. 28. Define lagging power factor. Answer: Power factor when current lags voltage. 29. Define leading power factor. Answer: Power factor when current leads voltage. 30. What is power in a three-phase circuit? Answer: P = √3 VL IL cosφ. UNIT 3: STATIC ELECTRIC MACHINES 1. What is the principle of a transformer? Answer: Electromagnetic induction. 2. Name the main parts of a transformer. Answer: Core, windings, tank. 3. What are the types of transformers based on construction? Answer: Core type and Shell type. 4. What is the EMF equation of a transformer? Answer: E = 4.44 f N φ. 5. Define voltage transformation ratio. Answer: Ratio of secondary to primary voltage. 6. What is the primary winding? Answer: The winding connected to the input supply. 7. What is the secondary winding? Answer: The winding connected to the load. 8. What is mutual flux in a transformer? Answer: The flux linking both primary and secondary windings. 9. What is transformer efficiency? Answer: Ratio of output power to input power. 10. What are core losses in a transformer? Answer: Hysteresis and eddy current losses. 11. What are copper losses in a transformer? Answer: Losses due to resistance in windings. 12. What is voltage regulation of a transformer? Answer: Change in secondary voltage from no-load to full load. 13. What is the ideal transformer assumption? Answer: No losses and 100% efficiency. 14. What are the types of losses in a transformer? Answer: Core and copper losses. 15. What is the function of the core in a transformer? Answer: Provide a path for magnetic flux. 16. What is leakage flux? Answer: Flux that does not link primary and secondary windings. 17. What is a step-up transformer? Answer: A transformer that increases voltage. 18. What is a step-down transformer? Answer: A transformer that decreases voltage. 19. Why is the transformer core laminated? Answer: To reduce eddy current losses. 20. What is the efficiency of an ideal transformer? Answer: 100%. 21. What is the use of bushings in a transformer? Answer: To insulate and support conductors. 22. What is the purpose of a cooling fan in a transformer? Answer: To dissipate heat generated. 23. What are the applications of a transformer? Answer: Transformers are used in voltage step-up and step-down, power distribution, and electrical isolation in circuits. UNIT 4: DC AND AC MACHINES 1. What is the working principle of a DC motor? Answer: whenever a current carrying conductor is placed in a uniform magnetic field , it experience a force. 2. What are the main parts of a DC motor? Answer: Armature, field winding, commutator. 3. What is the function of a commutator? Answer: Converts AC to DC in armature. 4. What is back EMF in a DC motor? Answer: EMF induced opposing applied voltage. 5. Name two types of DC motors. Answer: Series motor and shunt motor. 6. Define a DC series motor. Answer: Field winding in series with armature. 7. Define a DC shunt motor. Answer: Field winding in parallel with armature. 8. What determines the speed of a DC motor? Answer: Back EMF and flux. 9. What is the torque equation of a DC motor? Answer: T ∝ φ Ia. 10. What is the application of a DC series motor? Answer: Cranes, traction systems. 11. What is the application of a DC shunt motor? Answer: Lathes, fans. 12. What is the function of brushes in a DC machine? Answer: Transfer current to and from the armature. 13. What is armature reaction? Answer: Distortion of main field flux by armature flux. 14. What generates a rotating magnetic field in an induction motor? Answer: Three-phase AC supply. 15. What is the principle of a three-phase induction motor? Answer: Electromagnetic induction. 16. What is slip in an induction motor? Answer: The difference between synchronous and rotor speed. 17. What is the formula for slip? Answer: S = (Ns - Nr) / Ns. 18. What is a squirrel cage rotor? Answer: A rotor with short-circuited bars. 19. What is a wound rotor? Answer: A rotor with windings connected to external resistors. 20. What is the function of a stator in an induction motor? Answer: Provides mechanical protection and produces a rotating magnetic field 21. What is the function of a rotor? Answer: Induces current and produces torque. 22. What is synchronous speed? Answer: Speed of the rotating magnetic field. 23. What is the formula for synchronous speed? Answer: Ns = 120f / P. 24. What is the use of an induction motor? Answer: Pumps, fans, compressors. 25. What is the function of slip rings in a wound rotor? Answer: Connect external resistance. UNIT 5: ELECTRICAL INSTALLATIONS AND MEASURING INSTRUMENTS 1. What is the role of protection systems? Answer: Ensure safety and reliability of electrical systems. 2. What is LT switchgear? Answer: Low-tension switchgear and used to control and protect low-voltage circuits. 3. What is the function of an MCB? Answer: Protect circuits from overcurrent. 4. What is the function of an MCCB? Answer: Protect circuits from overcurrent and earth faults. 5. What is earthing? Answer: Connecting a system to the ground for safety. 6. What is the purpose of earthing? Answer: Prevent shock hazards. 7. What is the purpose of an SFU? Answer: To provide short-circuit protection. 8. What is the function of a fuse? Answer: Protect circuits by breaking under fault conditions. 9. What is the working principle of a PMMC instrument? Answer: Moving coil in a magnetic field produces torque. 10. What is MI instrument? Answer: A moving iron (MI) instrument is an electromechanical device used to measure AC and DC currents or voltages by utilizing the magnetic force on a soft iron piece. 11. What is PMMC instrument? Answer: A Permanent Magnet Moving Coil (PMMC) instrument is an electromechanical device that measures DC current or voltage using a permanent magnet and a moving coil. 12. What is the advantage of a PMMC instrument? Answer: High accuracy for DC. 13. What is the disadvantage of PMMC? Answer: Cannot measure AC. 14. What is the advantage of MI instruments? Answer: Measures both AC and DC. 15. What are the Applications of MI Instruments? Answer: § Measuring AC and DC voltages and currents. § Used in power systems and industrial controls. 16. What are the Applications of PMMC Instruments? Answer: § Measuring DC voltages and currents. § Used in laboratories for precise measurements. Dr.J.KARTIGEYAN Dean of Student Affairs