Moving Charges & Magnetism NEET PYQ — The Comparative-Radius Question Is Guaranteed
Moving Charges and Magnetism + Magnetism and Matter NEET PYQ (2015-2025). The comparative-radius question, the dia/para/ferro table, and 12 must-attempt PYQs with traps.
Moving Charges & Magnetism + Magnetism and Matter NEET PYQ Analysis (2015–2025)
One Question Type Is a Statistical Certainty: The Comparative-Radius Problem.
If you learn one thing from a decade of magnetism PYQs, learn this:
NTA gives you two particles — a proton and an alpha particle, say — entering a magnetic field under one shared condition (same velocity, same kinetic energy, or same accelerating voltage) and asks for the ratio of their circular radii. This question is a statistical certainty. It appears again and again because it tests one derivation (r = mv/qB) disguised four different ways, and it punishes students who memorise one version and assume it fits all.
The magnetism block is one of the most reliable scoring zones in NEET Physics — 3-5 questions per paper (12-20 marks, ~8-11% of Physics) — and it's more tractable than students fear. Its frameworks mirror Electrostatics almost exactly: if you understood the electric field from Coulomb's Law, the Biot-Savart Law will feel familiar. The difficulty isn't deep calculus; it's vector directions (right-hand rules), unit traps, and knowing which version of a formula to deploy.
We tracked the full testing pattern across both chapters from every NEET sitting 2015 to 2025. Moving Charges and Magnetism dominates at 65-75% of the block; Magnetism and Matter takes the rest. This is our sixth Physics PYQ analysis, after Electrostatics, Current Electricity, Ray Optics, Modern Physics, and Mechanics.
| 🎯 We analyzed every magnetism question NTA has asked. The app has them all — ready to play and practice. | |
|---|---|
| Magnetism is 3D — you can't learn the right-hand rule from a flat diagram, you have to rotate it. Logic Bloom's Playground turns the magnetism block into interactive games: fire a charge into a field and watch it curve, flip the charge sign and watch the force invert, build the field around a current-carrying wire, convert a galvanometer to an ammeter with a shunt. Then practice every PYQ from this analysis — line by line from NCERT + 10 years of PYQs, mapped to chapter topics. When the right-hand rule trips you, TarQ teaches the direction, and your Mistake Book catches every sign error. | Get the app → Free to start. |
Sub-Topic Frequency: Materials, Force on Charge, and Biot-Savart Lead
| Sub-topic | Frequency (10 yr) | Priority |
|---|---|---|
| Magnetic properties (dia/para/ferro) | 14 | Tier 1 — Critical |
| Force on a moving charge & circular motion | 12 | Tier 1 — Critical |
| Biot-Savart Law & field due to wire/loop | 11 | Tier 1 — Critical |
| Force between parallel conductors | 8 | Tier 2 — High |
| Torque on a loop & magnetic dipole moment | 7 | Tier 2 — High |
| Ampere's Law (solenoids, solid cylinders) | 6 | Tier 2 — High |
| Moving coil galvanometer (conversion) | 5 | Tier 3 — Moderate |
| Terrestrial magnetism & field lines | 3 | Tier 3 — Moderate |
| Motion in combined E and B fields | 3 | Tier 3 — Moderate |
The material-classification question (dia/para/ferro) is the single most frequent item — it appears almost annually, now usually as a match-the-column testing susceptibility ranges. Add force-on-charge and Biot-Savart and you've covered the three critical zones — 37 of the block's questions.
The Format Shift: From Algebra Marathons to Vector Reasoning
| Format | 2015–2018 | 2022–2025 |
|---|---|---|
| Numerical (multi-step algebra) | 75% | 55% |
| Conceptual / Assertion-Reason / Match | 25% | 45% |
The difficulty migrated from algebra to reasoning. Old questions made you integrate force over a square loop near a wire — pure computational endurance. Modern questions test whether you can apply a vector cross-product correctly, read a right-hand rule in 3D, or contrast dia/para/ferro properties in a single match grid. There's been a surge in Assertion-Reason and Match-the-Column, especially for Magnetism and Matter — NTA can test all three material types in one efficient question.
| 🎯 An electron and a proton feel the same field. Apply the right-hand rule the same way and you'll get the electron's force backwards. | |
|---|---|
| In F = q(v×B), the right-hand rule gives you the direction of v×B — but if the charge is an electron, the negative sign flips the force the opposite way. NTA always plants the non-inverted vector as an option to catch students who forget the charge sign. The fix isn't memorising — it's understanding that the force direction depends on the sign of q. Logic Bloom's Playground lets you fire positive and negative charges into the same field and watch them curve in opposite directions — with TarQ explaining why. Then practice every PYQ and let your Mistake Book catch the sign-flip errors before the exam does. | Play the forces → Free to start. |
The Comparative-Radius Cheat Sheet — Memorise This Cold
The guaranteed question. Everything hinges on which quantity is held constant. Start from r = mv/qB and substitute:
| 🎯 Radius of a Charged Particle in a Magnetic Field — All Four Cases | ||
|---|---|---|
| Shared condition | Formula | Radius depends on |
| Same velocity (v) | r = mv/qB | r ∝ m/q |
| Same momentum (p) | r = p/qB | r ∝ 1/q |
| Same kinetic energy (K) | r = √(2mK)/qB | r ∝ √m/q |
| Same accelerating voltage (V) | r = (1/B)√(2mV/q) | r ∝ √(m/q) |
The trap is using the wrong case. "Same KE" gives r ∝ √m/q; "same voltage" gives r ∝ √(m/q). For a proton vs alpha particle accelerated through the same V, the answer is 1:√2 — but if you wrongly use the KE formula, you get a different ratio and lose the mark. Read whether the shared quantity is velocity, momentum, KE, or voltage first.
Three Fundamental Rules That Decide Most Questions
| 📌 The Mechanics Rules NTA Tests Repeatedly | |
|---|---|
| Time period is independent of velocity | T = 2πm/qB. A faster particle traces a bigger circle in the same time. Speed and radius cancel out. NTA tests this as a conceptual surprise. |
| Magnetic force does ZERO work | The Lorentz force is always perpendicular to velocity, so it can't change speed — only direction. Kinetic energy stays constant in a pure magnetic field. A favourite assertion-reason. |
| Parallel wires: same direction ATTRACT | Currents in the same direction attract; opposite directions repel. This is the reverse of electrostatic charges (like repels like). NTA exploits the intuition clash. |
The Dia / Para / Ferromagnetic Table — The Annual Match Question
Tested almost every year, increasingly as a match-the-column. Know the susceptibility sign, the permeability, and the temperature behaviour:
| 🎯 Magnetic Materials Comparison | |||
|---|---|---|---|
| Property | Diamagnetic | Paramagnetic | Ferromagnetic |
| Susceptibility χ | −1 ≤ χ < 0 (small negative) | 0 < χ < small (small positive) | χ ≫ 1 (large positive) |
| Relative permeability μᵣ | 0 ≤ μᵣ < 1 | μᵣ > 1 | μᵣ ≫ 1 |
| In a field | Feeble repulsion (→ weaker field) | Feeble attraction (→ stronger field) | Strong attraction |
| Temperature | Independent of T | Curie's law (χ ∝ 1/T) | Curie-Weiss law |
The trap: confusing the small positive χ of paramagnets with the huge positive χ of ferromagnets in a match grid. And remember — only diamagnetism is temperature-independent; paramagnetism follows Curie's law (χ ∝ 1/T, a hyperbolic decay graph NTA loves to show).
The Galvanometer Conversion — NTA's Favourite Numerical
When the galvanometer is tested, NTA favours ammeter conversion 4-to-1 over voltmeter. Know both, but expect the shunt:
| Convert to | How | Formula |
|---|---|---|
| Ammeter (measures large current) | Small shunt resistance in parallel | S = IgG / (I − Ig) |
| Voltmeter (measures voltage) | Large resistance in series | R = V/Ig − G |
The two traps: (1) forgetting to convert the full-scale current Ig from mA to A before plugging in — a decimal-place disaster; (2) putting the total current I in the numerator instead of Ig. Ammeter = small shunt in parallel; voltmeter = large resistance in series. Don't swap them.
The 15 Formulas You Must Know Cold
| 🎯 15 Exam-Critical Formulas — Each Has Been Tested | ||
|---|---|---|
| 1. | Lorentz force: F = q(v×B) = qvB sinθ | Flip the direction for negative charges. |
| 2. | Radius: r = mv/qB = p/qB = √(2mK)/qB | The comparative-radius cheat sheet. |
| 3. | Time period: T = 2πm/qB | Independent of velocity and radius. |
| 4. | Force on conductor: F = BIL sinθ | Balance against mg in equilibrium problems. |
| 5. | Force between parallel wires: F/L = μ₀I₁I₂/2πd | Same direction → attract. |
| 6. | Biot-Savart: dB = (μ₀/4π)(Idl sinθ)/r² | The magnetic analogue of Coulomb's law. |
| 7. | Field at centre of N-turn loop: B = μ₀NI/2R | Tested directly (2025). |
| 8. | Solenoid: B = μ₀nI | n = turns per metre. Watch the mm→m unit trap. |
| 9. | Torque on loop: τ = MB sinθ = NIAB sinθ | Dipole moment M = NIA. |
| 10. | Dipole PE: U = −MB cosθ | Work to rotate = U_final − U_initial. |
| 11. | Ammeter shunt: S = I_gG/(I − I_g) | Convert I_g to amperes first. |
| 12. | Voltmeter: R = V/I_g − G | Large series resistance. |
| 13. | Permeability: μ = μ₀μᵣ = μ₀(1 + χ) | Don't stop at μᵣ — multiply by μ₀. |
| 14. | Velocity selector: v = E/B | Undeflected charge in crossed fields. |
| 15. | Curie's law: χ ∝ 1/T (paramagnetic) | Hyperbolic decay graph. |
Cross-Chapter Connections
| Cross-Chapter Link | What It Tests | Example |
|---|---|---|
| Magnetism + Mechanics | Balancing magnetic force vs weight | A current-carrying rod suspended in a field: BIL = mg (or mg sinθ on an incline). |
| Magnetism + Modern Physics | Magnetic moment of an orbiting electron | Substitute Bohr's quantised angular momentum into M = IA → M = nhe/4πm. |
| Magnetism + Current Electricity | Galvanometer, current in conductors | Shunt/series resistance conversions, force on current-carrying wires. |
| Magnetism + EMI | Source of work in repulsion | When a diamagnetic rod is pushed out of a field, the work comes from the current source. |
Re-NEET 2026 / NEET 2027 Predictions
All predictions exclude the deleted topics (cyclotron, toroid derivation, Oersted's experiment).
Top 5 Sub-Topics Most Likely to Appear
| # | Predicted Topic | Why It's Due |
|---|---|---|
| 1 | Comparative radius under same voltage | The r ∝ √(m/q) version was absent in 2024 — overdue. Proton vs alpha through the same V → 1:√2. |
| 2 | Biot-Savart superposition (complex geometry) | Field at the centre of a semicircular arc + straight segments. Vector addition of contributions. |
| 3 | Assertion-Reason on magnetic materials | Curie's law: paramagnetism ∝ 1/T while diamagnetism is temperature-independent. |
| 4 | Galvanometer → ammeter conversion | Shunt resistance numerical, possibly asking the effective ammeter resistance GS/(G+S). |
| 5 | Equilibrium of parallel wires | Three parallel conductors — net force on the middle wire by superposition. |
2 Concepts Due for a Return (still in syllabus)
| Concept | Status | Likely Format |
|---|---|---|
| Velocity selector (v = E/B) | Last tested heavily 2020 | Undeflected charge in crossed E and B fields. |
| Work to rotate a dipole | Periodic | Energy to rotate a loop/magnet from stable (0°) to unstable (180°): W = 2MB. |
Moving Charges & Magnetism NEET PYQs (2015–2025) — 12 Questions You Must Attempt
These 12 represent NTA's most-repeated magnetism patterns (deleted topics excluded). For each, the specific trap is explained — the mistake that costs you 5 marks (4 lost + 1 negative).
| 📌 12 Must-Attempt Magnetism PYQs — With the NTA Trap Explained | |
|---|---|
| 1. Galvanometer → Ammeter (2025) | 100 Ω galvanometer, full-scale 1 mA. Shunt for a 0-10 A ammeter? Answer: 0.01 Ω. Trap: Convert 1 mA to 10⁻³ A before subtracting from 10 A in S = I_gG/(I − I_g). |
| 2. Field at Coil Centre (2025) | 100 turns, radius 10 cm, current 7 A. Field at centre? Answer: 4.4 mT. Trap: Forgetting the N (turns) factor in B = μ₀NI/2R — it's per turn × N. |
| 3. Dia/Para/Ferro Match (2024) | Match materials to susceptibility ranges. Answer: Dia: −1≤χ<0; Para: 0<χ<small; Ferro: χ≫1. Trap: Confusing the small positive χ of paramagnets with the huge positive χ of ferromagnets. |
| 4. Bent Magnet Moment (2024) | Bar magnet (moment M) bent at the middle to a 60° angle. New moment? Answer: M/2. Trap: Each half has moment M/2; the vector sum of two M/2 arms at 60° gives M/2 (use the resultant, not the scalar sum). |
| 5. Solenoid Field + Unit Trap (2022) | Solenoid, 100 turns per mm, 1 A. Field at centre? Answer: 12.56×10⁻² T. Trap: "100 turns per mm" = 100,000 turns per metre. Convert before B = μ₀nI. |
| 6. Lorentz Force, Electron Sign (2021) | Electron with v and F given — find B. Answer: Requires sign inversion. Trap: For an electron q = −1, so F = −(v×B). Forgetting the negative gives the wrong B direction. |
| 7. Permeability from Susceptibility (2020) | Iron rod χ = 599, field 1200 A/m. Absolute permeability? Answer: 2.4π×10⁻⁴ T·m/A. Trap: Computing μᵣ = 1+χ = 600 and stopping — you must multiply by μ₀ for absolute permeability. |
| 8. Comparative Radius, Same Voltage (2019) | Proton and alpha through the same V, enter B perpendicular. Ratio of radii? Answer: 1:√2. Trap: Using the KE formula (r ∝ √m/q) instead of the voltage formula (r ∝ √(m/q)). The shared quantity decides. |
| 9. Diamagnetic Repulsion Work (2018) | Diamagnetic rod pushed up out of the field. Where does the work come from? Answer: The current source. Trap: Conceptual — moving a diamagnet from strong to weak field needs energy, supplied by the electromagnet's current source. |
| 10. Square Loop near Wire (2016) | Square loop coplanar with a long straight wire. Net force? Answer: Attractive, toward the wire. Trap: Forces on the two perpendicular sides cancel; net force = difference between near (attract) and far (repel) segments. |
| 11. Electron Along Parallel Fields (2023) | E and B along the same direction; electron projected along them. What happens? Answer: Speed decreases. Trap: v∥B → magnetic force is zero (sin0 = 0). Only the electric force acts, decelerating the electron. No helical motion. |
| 12. Parallel Wire Force (2022) | Two wires, 5 A and 10 A, 10 cm apart. Force per unit length? Answer: 1×10⁻⁴ N/m, attractive. Trap: Same-direction currents attract (opposite of charges). Use F/L = μ₀I₁I₂/2πd. |
| 🎯 These are 12 of the 200+ magnetism PYQs in the app. Drill all of them. | |
|---|---|
| Every question above is inside Logic Bloom — along with hundreds more from NCERT + 10 years of PYQs, mapped into chapter topics you can learn and master. Play through the simulations first: fire charges into fields, build the field around a wire, convert a galvanometer with a shunt. When you get a question wrong, TarQ teaches you the concept — not the answer. Your Mistake Book tracks exactly which traps catch you — the charge sign, the unit conversion, the wrong radius formula. Then take it all into Battleground — 1v1 duels under real exam pressure. Get Logic Bloom — Free to start → |
How to Prepare Based on the Data
| 📌 Data-Driven Preparation Strategy for Magnetism NEET 2027 | |
|---|---|
| Master the comparative-radius cheat sheet | Four cases — same v, p, K, or V. Read which quantity is shared FIRST, then pick the formula. This single question type is a statistical certainty. |
| Memorise the dia/para/ferro table | Susceptibility sign and size, permeability, temperature behaviour. It's tested almost every year, now as a match grid. Only diamagnetism is temperature-independent. |
| Lock the three fundamental rules | T is independent of velocity; magnetic force does zero work; parallel same-direction currents attract (opposite of charges). Each is a conceptual NTA favourite. |
| Watch the charge sign and the units | Electrons invert the force direction. Solenoid turns are per metre (mm→m trap). Galvanometer current is in amperes (mA→A trap). These three errors cost the most marks. |
| Don't multiply by μ₀ at the end? You lose the mark | μ = μ₀(1+χ). Computing μᵣ and stopping is the permeability trap. Absolute permeability always needs the μ₀ factor. |
| Play the fields, practice every PYQ, track your slips | Logic Bloom's Playground turns magnetism into interactive games — fire charges, build fields, convert galvanometers — with TarQ guiding the right-hand rule. Then practice every PYQ, mapped chapter by chapter, with your Mistake Book catching sign and unit errors. Then test it in Battleground under exam pressure. Free to start. |
Done analysing? Now play, understand, and master.
| 🎯 3-5 questions per paper. The comparative-radius question is guaranteed. The dia/para/ferro match appears almost every year. The patterns are here. The practice is in the app. | |
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| 🎮 Playground Understand through games — with TarQ |
Every magnetism concept as an interactive game — fire a charge into a field and watch it curve, flip the sign and watch the force invert, build the field around a current-carrying wire, convert a galvanometer with a shunt. Chapter maps break each topic into concept games → readings → MCQs. Line by line from NCERT + 10 years of PYQs, all inside. When you're stuck, TarQ teaches the right-hand rule. Mistake Book catches sign errors before the exam does. Get the app → |
| ⚔️ Battleground Score through practice — 1v1 duels |
Take the concepts you understood in Playground and test them under real time pressure. Challenge a friend or get matched live. 10 timed questions per match across Physics, Chemistry, Biology. ELO climbs through 6 tiers: Bronze → Silver → Gold → Platinum → Diamond → Archeon. Get the app → |
| Understand through games. Score through practice. Get Logic Bloom — Free to start → |
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FAQs — Moving Charges & Magnetism NEET PYQ
Q1: How many questions come from magnetism in NEET?
The magnetism block (Moving Charges and Magnetism + Magnetism and Matter) delivers 3-5 questions per paper — 12 to 20 marks, roughly 8-11% of Physics. Moving Charges and Magnetism dominates at 65-75% of the block; Magnetism and Matter takes the remaining 25-35%.
Q2: What is the most guaranteed question in magnetism?
The comparative-radius question — two particles (like a proton and an alpha particle) entering a magnetic field under a shared condition, asking for the ratio of their circular radii. The key is reading whether they share the same velocity (r ∝ m/q), momentum (r ∝ 1/q), kinetic energy (r ∝ √m/q), or accelerating voltage (r ∝ √(m/q)).
Q3: Why does a magnetic force do no work?
The magnetic Lorentz force is always perpendicular to the particle's velocity (F = qv×B). A force perpendicular to motion changes direction but never speed, so it does zero work and the kinetic energy stays constant. This is why a charged particle moves in a circle at constant speed in a uniform magnetic field.
Q4: Do parallel current-carrying wires attract or repel?
Wires carrying current in the same direction attract; wires carrying current in opposite directions repel. This is the reverse of electrostatic charges, where like charges repel — a common source of confusion that NTA exploits.
Q5: Are there actual magnetism PYQ questions to practice?
Yes — this article contains 12 representative PYQs with the NTA trap explained for each (deleted syllabus topics excluded). For the full set of 200+ magnetism PYQs mapped to chapter topics with TarQ teaching and a Mistake Book tracking your errors, download Logic Bloom. Free to start.
