JEE Advanced 2026 Paper 2 — Full Mock Test (54 Questions, 180 Marks)
Mathematics · Physics · Chemistry
આ MCQ મોડ્યુલ આના પર આધારિત છે: Magnetism Gauss Law
ટોપિક 20 / 38
Magnetism Gauss Law
🎓 Class 12
Physics
CBSE
Theory
Ch 5 – Magnetism and Matter
⏱ ~14 min
🌐 ભાષા:
🧠 AI-આધારિત MCQ મૂલ્યાંકન
▲
📝 વર્કશીટ / મૂલ્યાંકન
▲
આ મૂલ્યાંકન આના પર આધારિત હશે: Magnetism Gauss Law
મૂલ્યાંકન બનાવવામાં તેમની સામગ્રી સામેલ કરવા ચિત્રો, PDF અથવા Word દસ્તાવેજ અપલોડ કરો.
Magnetism Gauss Law
5.3 Magnetism and Gauss's Law
For an electric field, Gauss's law states that the total electric flux through any closed surface equals \(q_{enc}/\varepsilon_0\). For magnetic fields the situation is fundamentally different - because isolated magnetic poles do not exist, no closed surface can ever enclose a net "magnetic charge".
Gauss's law for magnetism: The total magnetic flux through any closed surface S is zero.
\[\oint_S \vec B\cdot d\vec A = 0\]
This is one of Maxwell's four equations, and it is exactly equivalent to the statement: magnetic monopoles do not exist.Pictorially, every magnetic field line that enters a closed surface must also leave it. If a bar magnet is placed inside a Gaussian sphere, lines emerging from N exit the sphere, but precisely the same number re-enter at S - net flux is zero.
5.4 Earth's Magnetism
The Earth itself behaves like a giant magnetic dipole. To a first approximation we may imagine a powerful bar magnet buried at its centre, tilted by about 11° from the rotation axis. The geomagnetic field at the surface is small (≈ 25-65 μT) but it is what allows compasses to work and shields life from the solar wind.
Important convention: The Earth's geographic North Pole is actually a magnetic south pole - field lines come out of the geographic south and re-enter at the geographic north. The compass "N" is attracted to that magnetic-south region, which we conventionally still call "magnetic north".
5.4.1 The three geomagnetic elements
At any point on the Earth's surface, the local magnetic field \(\vec B\) is fully specified by three numbers, the geomagnetic elements.
- Magnetic declination, D - the angle in the horizontal plane between geographic north (true north) and magnetic north (compass direction).
- Magnetic dip / inclination, I (or angle of dip δ) - the angle which the resultant field B makes with the horizontal plane.
- Horizontal component, H = \(B_E \cos I\), where \(B_E = |\vec B|\) is the total field. The vertical component is \(Z = B_E \sin I\).
\[B_E^2 = H^2 + Z^2,\quad \tan I = \dfrac{Z}{H}\]
5.4.2 Variation of dip with latitude
At the magnetic equator (the line where I = 0) the field is purely horizontal; H = \(B_E\), Z = 0. At the magnetic poles (I = 90°) the field is vertical; H = 0, Z = \(B_E\). For a dipole approximation, dip and magnetic latitude λ are related by \(\tan I = 2\tan\lambda\).
| Location | BE (μT) | D | I (dip) |
|---|---|---|---|
| Magnetic equator | ~30 | 0° | 0° |
| Mumbai (India) | ~38 | ~0° (≈ magnetic and true N coincide) | ~24° |
| Delhi | ~46 | ~1° W | ~41° |
| Magnetic pole (Arctic) | ~60 | undefined | ~90° |
Worked Example 5.3 - Total field from H and I
Example 5.3 L3 Apply
At a place, H = 30 μT and dip I = 60°. Find the total Earth's field BE and its vertical component Z.
BE = H/cos I = 30/cos 60° = 30/0.5 = 60 μT.
Z = BE sin I = 60 × sin 60° = 60 × 0.866 ≈ 52 μT.
Check: H² + Z² = 900 + 2700 ≈ 3600 = (60)² ✓.
Worked Example 5.4 - Magnetic latitude from dip
Example 5.4 L4 Analyse
The magnetic dip at a place is 30°. Estimate the magnetic latitude λ of the place using the dipole approximation.
Use tan I = 2 tan λ ⇒ tan λ = ½ tan 30° = ½(0.577) = 0.289.
So λ ≈ 16.1°. The place is about 16° from the magnetic equator.
Interactive: Geomagnetic Elements L3 Apply
Adjust H and I; see B, Z and a vector diagram update.
BE = 42.4 μT | Z = 30.0 μT
Activity 5.2 - Find your local declinationL5 Evaluate
- Use a magnetic compass to find magnetic north at noon.
- Use shadow of a vertical stick at solar noon to mark true north.
- Measure the angle between the two ⇒ that is the local declination D.
In your area, do you expect D > 0 (east) or D < 0 (west)? Compare your value with the published map value.
D varies smoothly with longitude. In most of mainland India, the magnetic north is just west of true north (D ≈ 0°-2° west). Your measured value should be within a few degrees of the published value.
Competency-Based Questions L1-L6
A geomagnetic survey records BE = 50 μT and dip I = 53° at a location.
1. The horizontal component H equals (sin 53° = 0.8, cos 53° = 0.6): L3 Apply
(b) H = BE cos I = 50 × 0.6 = 30 μT.
2. State Gauss's law for magnetism in words and as an equation. L1 Remember
The net magnetic flux through any closed surface is zero. \(\oint \vec B\cdot d\vec A = 0\). Equivalent to: magnetic monopoles do not exist.
3. Why does a compass at the magnetic north pole rest in any direction (i.e. become useless)? L2 Understand
Because at the magnetic pole I ≈ 90°, so H = BE cos 90° ≈ 0. With no horizontal component, the compass needle has no preferred horizontal direction.
4. A "dip circle" measures dip but the reading depends on its orientation. Why must it be set in the magnetic meridian? L4 Analyse
A dip circle measures the apparent dip in its plane. Only when the plane contains the field B (i.e. is the magnetic meridian) does it record the true dip I. In any other plane the projection of B is smaller and the apparent dip is larger - giving an incorrect reading.
5. Compose a half-page note on why understanding declination is important for navigation, aviation and pipeline surveying. L6 Create
Sample points: (i) ships and aircraft compute true bearings from magnetic compass readings using D; (ii) D varies with location and time (secular variation), so updated geomagnetic charts are essential; (iii) pipelines and tunnels under construction must be aligned to true geographic axes - errors in D translate into kilometres of misalignment over long distances; (iv) modern aviation cross-checks GPS with gyrocompass and magnetic compass for redundancy.
Assertion-Reason Pairs L4 Analyse
Options: (A) Both true, R correct explanation. (B) Both true, R not the explanation. (C) A true, R false. (D) A false, R true.
Assertion: The total magnetic flux through a closed surface enclosing a bar magnet is zero.
Reason: Magnetic field lines form closed loops; every line that enters the surface must also leave.
(A). Reason directly explains the assertion - this is Gauss's law for magnetism.
Assertion: A compass placed at the magnetic equator rests pointing horizontally.
Reason: At the magnetic equator, dip I = 0 so the field is purely horizontal.
(A). True; horizontal field aligns the needle horizontally.
Assertion: Earth's geographic north pole and magnetic north pole are the same place.
Reason: Compasses always point to true north.
(D). Both statements are false: the two poles are separated by ~11°, and compasses point to magnetic north (= D away from true north). Wait - "D" describes the difference, neither A nor R is true. Best fit: both false.
Frequently Asked Questions - Magnetism Gauss Law
What is the main concept covered in Magnetism Gauss Law?
In NCERT Class 12 Physics Chapter 5 (Magnetism and Matter), "Magnetism Gauss Law" covers the core principles and equations students need for board exam success. The MyAiSchool lesson explains the topic with definitions, derivations, worked examples, and interactive simulations. Key formulas and dimensional analysis are included to build conceptual depth and problem-solving skills aligned with the CBSE 2025-26 syllabus.
How is Magnetism Gauss Law useful in real-life applications?
Real-life applications of "Magnetism Gauss Law" from NCERT Class 12 Physics Chapter 5 include electronics, communication systems, medical imaging, solar energy, semiconductor devices, and modern technology. The MyAiSchool lesson links every concept to a tangible example so students see physics as a problem-solving framework for the physical world, not as abstract formulas.
What are the key formulas in Magnetism Gauss Law?
Key formulas in "Magnetism Gauss Law" (NCERT Class 12 Physics Chapter 5 Magnetism and Matter) are derived step-by-step in the MyAiSchool lesson. Students should memorize the final formula AND understand its derivation for full board marks. Each formula is listed with its dimensional formula, SI unit, applicability range, and common pitfalls. The Summary section at the end of each part includes a quick-reference formula card.
How does this part connect to other parts of Chapter 5?
NCERT Class 12 Physics Chapter 5 (Magnetism and Matter) is structured so each part builds on the previous one. "Magnetism Gauss Law" connects directly to neighbouring parts via shared definitions, units, and methodology. The MyAiSchool lesson cross-references related concepts with internal links so students can navigate the whole chapter as one connected story rather than disconnected fragments.
What types of CBSE board questions come from Magnetism Gauss Law?
CBSE board questions from "Magnetism Gauss Law" typically include: (1) 1-mark MCQs on definitions and formulas, (2) 2-mark short-answer derivations or applications, (3) 3-mark numerical problems with units, (4) 5-mark long-answer derivations followed by application. The MyAiSchool lesson tags each Competency-Based Question (CBQ) with Bloom level (L1-L6) so students know how to study for each weight.
How can students use the interactive simulation effectively?
The interactive simulation in the "Magnetism Gauss Law" lesson allows students to adjust input parameters (sliders or selectors) and see physical quantities update in real time. To use it effectively: (1) try extreme values to understand limiting cases, (2) compare with the analytical formula, (3) check unit consistency, (4) test special configurations from worked examples. The simulation reinforces conceptual intuition that pure formula manipulation cannot.
AI ટ્યુટર
Physics Class 12 Part I – NCERT (2025-26)
તૈયાર
🎯 Physics ની પ્રેક્ટિસ કરો
તમે જે ભણ્યા તેનું પૂરું પેપર આપો, પ્રશ્ન દીઠ તપાસાયેલું.
બોર્ડ પરીક્ષા સેમ્પલ પેપર
Physics
CBSE
Physics — CBSE Class XII Sample Paper 1 (2025-26)
Section A · Section B · Section C · Section D · Section E
મોક પરીક્ષાઓ
JEE Advanced 2026 Paper 2 — Full Mock Test (54 Questions, 180 Marks)
Mathematics · Physics · Chemistry
JEE Main Mock Test — Full Paper (75 Questions, 300 Marks)
Part A - Physics (Section A) · Part A - Physics (Section B) · Part B - Chemistry (Section A) · Part B - Chemistry (Section B) · Part C - Mathematics (Section A) · Part C - Mathematics (Section B)
🎁 Join our community and get free AI credits!