EE479 Questions PDF

1. Difference between soft and hard magnetic materials Soft magnetic materials: They magnetize easily but lose their magnetism quickly. Example: Iron. Hard magnetic materials: They are difficult to magnetize but retain their magnetism for a long time. Example: Neody...

1. Difference between soft and hard magnetic materials Soft magnetic materials: They magnetize easily but lose their magnetism quickly. Example: Iron. Hard magnetic materials: They are difficult to magnetize but retain their magnetism for a long time. Example: Neodymium magnets. 2. What is magnetic force? Magnetic force is the force exerted on a charged particle moving in a magnetic field or on a current- carrying conductor placed in a magnetic field. 3. What is a magnetic field? A magnetic field is a region around a magnet or current-carrying conductor where magnetic forces can be detected. It is represented by magnetic field lines. 4. How to determine the direction of magnetic force? The direction of the magnetic force can be determined using the right-hand rule: Point your thumb in the direction of current (or velocity of positive charge). Point your fingers in the direction of the magnetic field. The force direction will be perpendicular to your palm. 5. Differences between electric field and magnetic field Electric Field Magnetic Field Created by electric charges (static or moving). Created by moving charges or magnetic materials. Acts along the direction of the field. Acts perpendicular to the direction of the field. Measured in volts per meter (V/m). Measured in teslas (T). 6. How do we calculate the magnetic force on a current-carrying wire? 7. Please describe the magnetic flux equation 8. What is eddy current? Eddy currents are loops of electric current induced within a conductor when it is exposed to a changing magnetic field. They cause energy loss in the form of heat. 9. How do we measure distance using eddy current? Eddy current sensors measure distance by detecting changes in the magnetic field caused by proximity to a conductive surface. The sensor outputs a voltage proportional to the distance. 10. Please describe the Hall effect The Hall effect occurs when a magnetic field is applied perpendicular to a current-carrying conductor, creating a voltage (Hall voltage) across the conductor due to the deflection of charge carriers. 11. Working principles of Hall effect sensor A Hall effect sensor detects the presence and magnitude of a magnetic field by measuring the Hall voltage generated when the field interacts with current-carrying charges in a semiconductor. 12. Difference between linear and threshold Hall effect sensors Linear Hall effect sensor: Outputs a voltage proportional to the magnetic field strength. Threshold Hall effect sensor: Switches on or off when the magnetic field exceeds a certain threshold. 13. Definition of hysteresis loss Hysteresis loss is the energy lost as heat in a magnetic material during the magnetization and demagnetization cycles. 14. Differences between hysteresis loss and eddy current loss Hysteresis Loss Eddy Current Loss Due to repeated magnetization cycles. Due to circulating currents in the conductor. Depends on the material’s hysteresis loop. Depends on the magnetic field and material conductivity. 15. What types of transformers do you know? Step-up transformer Step-down transformer Isolation transformer Autotransformer 16. What is an autotransformer? An autotransformer is a transformer with a single winding that acts as both the primary and secondary winding, allowing energy transfer through both induction and direct connection. 17. Describe the EMF equation of a transformer 18. What is the phasor diagram of a transformer? A phasor diagram of a transformer represents the relationship between voltages, currents, and flux in both primary and secondary windings using vector quantities. 19. What is full load voltage regulation in transformers? Voltage regulation is the percentage difference between the no-load and full-load secondary voltages of a transformer. 20. How do we calculate the efficiency of a transformer? 21. What is a transformer tap? A transformer tap is a connection point on a winding that allows adjustment of the voltage ratio. 22. How can we build a three-phase transformer? Three-phase transformers can be built by combining three single-phase transformers or using a single core with three windings for each phase. 23. What is a Y connection? A Y connection (wye) connects three windings with a common neutral point. 24. What is a Δ connection? A Δ connection (delta) connects the windings in a closed-loop triangle configuration. 25. What types of three-phase transformer connections do you know? Y-Y, Y-Δ, Δ-Y, Δ-Δ 26. Advantages of a Delta three-phase system No neutral is needed. Provides higher reliability in case of phase failure. 27. What determines the generated torque in a rotating magnetic field? The generated torque depends on the strength of the magnetic field, current in the windings, and the relative position of the magnetic field and rotor. 28. Voltage induced in a rotating loop (equation) 29. Power flow diagram, what is it? A power flow diagram shows the distribution of input power in a system, including losses and useful output power. 30. Relationship between electrical frequency and mechanical speed