eee-1109 EEE-1109 Basic Electrical Engineering That’s a very focused request! Understanding the types of questions that appear frequently in exams, along with the required preparation strategy, is key to success.
Drawing on the term exam data provided (covering EEE-1109 Basic Electrical Engineering from 2016 through 2024) and the foundational content on magnetic circuits, here is the comprehensive breakdown of the Magnetic Circuits and Coupling section (Section 3), followed by an analysis of the question and the foundational content on magnetic circuits, here is the comprehensive breakdown of the Magnetic Circuits and Coupling section (Section 3), followed by an analysis of the question types and preparation advice.
I. Magnetic Circuits and Coupling: Term Questions and Appearance History
The sources categorize the magnetic circuit questions into three main areas: Fundamental Concepts and Comparison, Losses and Hysteresis, and Coupling/Energy/Calculations.
A. Fundamental Concepts, Laws, and Comparisons (Section 3.1)
This category focuses heavily on definitions and the core analogy between electric and magnetic circuits.
| Definition/Statement | Year(s) of Appearance |
|---|---|
| Define reluctance. | 2016, 2017, 2018, 2019, 2024 |
| Define permeability. | 2017, 2018, 2019 |
| Define permeance. | 2016 |
| Define mmf (Magnetomotive Force). | 2016 |
| Define Flux density. | 2024 |
| Define Magnetizing force. | 2024 |
| What are the basic differences between electric circuit and magnetic circuit? / Differentiate between electrical circuit and magnetic circuit. | 2016, 2017, 2019, 2023 |
| State and explain the Ampere’s circuital law (for magnetic circuit). | 2017, 2019, 2022, 2023 |
| State and explain Biot Savart law for a magnetic circuit. | 2017, 2019 |
| Show that the magnetic flux density at any specified distance from a long straight current carrying conductor is . (Derivation) | 2016 |
| Write down some applications of magnetic circuit. | 2019 |
B. Losses and Hysteresis (Section 3.2)
This category involves conceptual understanding and explanation of non-ideal magnetic behavior.
| Question/Task | Year(s) of Appearance |
|---|---|
| Explain hysteresis loss and eddy current loss. How to minimize these losses? | 2016 |
| Explain hysteresis loss and eddy current loss in a magnetic circuit. | 2018, 2022 |
| What is hysteresis loop? Show the difference between soft and hard materials using a hysteresis loop with coercive force and retentivity. | 2023 |
C. Coupling, Energy, and Calculations (Sections 3.3 and 3.4)
These questions test the derivation of key concepts and the ability to apply magnetic circuit formulas to solve numerical problems.
| Question/Task | Year(s) of Appearance |
|---|---|
| Define magnetic coupling. Derive the expression of the coefficient of magnetic coupling. | 2016, 2019 |
| Define coupled circuits. | 2022, 2023 |
| Derive the expression of coefficient of magnetic coupling and show that the maximum value of the coefficient of magnetic coupling could be unity. | 2023 |
| Derive the expression of energy stored in a toroid and show that . | 2016 |
| Determine the secondary current for the transformer… if the flux in the core is Wb. (Calculation) | 2016 |
| Find the magnetomotive force around a long straight conductor. | 2017 |
| Find the current required to established a flux Wb in the magnetic circuit shown. (Calculation) | 2018 |
| Find the magnetic flux for the series magnetic circuit in the following figure for the specified impressed mmf. (Calculation) | 2019 |
| Find the current I required to establish a magnetic flux (Calculation based on core dimensions and turns). | 2022 |
| Determine the current that the 500 turn-magnetising coil on the left limb should carry so that a flux of Wb is produced in the right limb. (Calculation) | 2023 |
| A rectangular iron core is shown… Find the flux in the air gap. (Calculation) | 2024 |
II. Analysis of Question Types and Exam Preparation
Based on the provided history, the magnetic circuit section consistently emphasizes specific theoretical concepts and numerical problem-solving.
1. Most Common Question Types
The exam questions related to magnetic circuits fall primarily into three frequent categories:
A. Core Definitions (High Frequency) Definitions of key terms are nearly guaranteed on the exam.
- Reluctance: Appeared in five of the seven years documented.
- Permeability: Appeared frequently between 2017 and 2019.
- Flux density and Magnetizing force definitions recently appeared in 2024.
B. Foundational Laws and Comparisons (Critical Theory) These questions require explanation and differentiation, not just definition.
- Differences between Electric and Magnetic Circuits: This is a highly recurring theoretical question, appearing in 2016, 2017, 2019, and 2023. The sources provide the key differences, such as the constancy of resistance versus the variability of reluctance ( changes with ) and the continuous energy expenditure in electric circuits versus the initial energy requirement in magnetic circuits.
- Ampere’s Circuital Law: This law is crucial for theory and derivation, appearing in 2017, 2019, 2022, and 2023.
C. Numerical Problem Solving (Application) Calculation problems based on magnetic circuit geometry are highly consistent, appearing every year from 2018 to 2024, with another example in 2016. These calculations require applying the Ohm’s Law analogy () to composite circuits.
- Series Circuits: Problems typically require calculating the total required Ampere-turns (AT) for a core with multiple segments (like iron and air gap).
- Parallel/Series-Parallel Circuits: More complex questions, like those from 2023 and 2024, require handling flux division and combining m.m.f. requirements for parallel paths and common paths, similar to Examples 6.19, 6.21, and 6.22 provided in the sources.
2. Preparation Strategy for the Magnetic Circuit Section
To prepare effectively for the exam based on these sources, you should focus on both rote memorization of definitions and the ability to execute problem-solving steps:
1. Master the Vocabulary and Analogies:
- Know all definitions cold: Ensure you can define reluctance, permeability, permeance, MMF, flux density, and magnetizing force accurately.
- Internalize the Comparison Table: Be prepared to explicitly list and explain the nine similarities and three key differences between electric and magnetic circuits, especially noting why reluctance is not constant (due to varying with ).
2. Focus on Core Theory and Derivations:
- Be ready to state and explain Ampere’s Circuital Law and understand its application (e.g., finding for a long straight conductor).
- Understand and explain the concepts of hysteresis loss and eddy current loss, along with methods to minimize them.
- Practice the derivation for the coefficient of magnetic coupling.
3. Practice Numerical Problems Extensively:
- The most frequent numerical question involves calculating the Total Ampere-Turns (AT) required to establish a specific flux () in a core.
- Practice the standard procedure for composite circuits: (1) Find for each segment ( for air, for material), (2) Calculate AT for each segment (), and (3) Sum the ATs for series circuits.
- Be prepared for Series-Parallel circuits, where you must determine the flux in the central limb, calculate the m.m.f. for the common path, and then calculate the m.m.f. for only one of the parallel paths before summing.
A good way to visualize this preparation is like assembling a model airplane: definitions are the foundational pieces, the comparisons and laws are the structural framing, and the numerical problems are the functional assembly, requiring you to use all the preceding steps correctly to reach the final goal.