| Pattern | Years Seen | Typical Question Type | Common Trap |
|---|---|---|---|
| E inside conductor vs insulator | 2019, 2022, 2024 | "At r = R/2 from center, E = ?" | Assume E=0 inside any sphere |
| Capacitor + dielectric (battery scenario) | 2018, 2020, 2023 | Energy/voltage change after dielectric insertion | Confusing connected vs disconnected |
| Dipole field ratio (axial:equatorial) | 2017, 2019, 2021 | Ratio of fields at same r | Forgetting factor of 2 |
| Gauss's law — infinite wire/plane | 2016, 2018, 2020 | Derive E or calculate for given λ/σ | Wrong symmetry argument |
| Series/parallel capacitor combinations | 2019, 2022, 2023 | Equivalent capacitance, charge distribution | Series gives same charge, not same voltage |
| Equipotential surfaces | 2018, 2021 | Work done, angle with field lines | Thinking work done ≠ 0 on equipotential |
| Coulomb's law + superposition | 2017, 2020, 2024 | Net force on charge due to multiple charges | Sign error in vector addition |
Exam Strategy:
- For capacitor questions: first identify whether battery is connected or disconnected — this determines whether V or Q is constant.
- For dipole questions: always write both formulas first, then check which region is asked.
- For Gauss's law: draw the Gaussian surface and label the symmetry argument before writing any equation.