Force and Torque Due To Magnetic Field

1. Magnetic Force:

• Lorentz Force

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Definition, mathematical expression (F = qvB sinθ), direction using the right-hand rule, force on a positive and negative charge.

• Examples: Motion of a charged particle in a magnetic field.

• Magnetic Force on a Moving Charge:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key Concepts: Force experienced by a moving charge in a magnetic field, explanation using Lorentz force equation.

• Examples: Trajectory of a charged particle in a magnetic field.

• Magnetic Force on a Current Carrying Conductor:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key Concept: Force acting on a current-carrying conductor placed in a magnetic field, direction using Fleming’s left-hand rule.

• Examples: Forces on a straight conductor, a circular loop.

• Magnetic force between two current-carrying conductors:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Parallel and perpendicular conductors, attractive and repulsive forces, concept of magnetic field lines.

• Examples: Calculation of force between various configurations.

• Magnetic force on a Magnetic Dipole:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Magnetic dipole moment, torque experienced by a magnetic dipole in a magnetic field.

• Examples: Potential energy of a magnetic dipole, bar magnet suspended in a magnetic field.

2. Magnetic Field:

• Magnetic field due to a current carrying conductor:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Biot-Savart law, mathematical expression for the magnetic field, field due to straight wire, circular loop, solenoid.

• Examples: Calculating the magnetic field at various points.

• ** Magnetic Field due to a Solenoid**:

• Reference: NCERT class 12, chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Solenoid as a long coil, field inside and outside a solenoid, comparison with field due to a bar magnet.

• Examples: Magnetic field strength inside a solenoid.

• ** Magnetic Field due to a Toroid**:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Toroid as a coil wound in a circular fashion, field inside and outside the toroid.

• Examples: Determination of magnetic field at the center of toroid.

• ** Magnetic Field inside a long straight solenoid**:

• Reference: NCERT class 12, chapter - Magnetic effects of current and magnetism.

• Key concepts: Uniform magnetic field inside a long straight solenoid, its magnitude, and direction.

• Examples: Calculating the field strength inside a given solenoid.

• ** Magnetic Field due to a bar magnet**:

• Reference: NCERT class 12, chapter - Magnetic Effects of Current and Magnetism.

• Key concepts: Magnetic field lines, field pattern of a bar magnet.

• Examples: Determining the magnetic field at various points around a bar magnet.

3. Magnetic Torque:

• Torque on a Current loop in a magnetic field:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Torque experienced by a current loop, formula for torque (τ = NIAB sinθ), direction using the right-hand rule.

• Examples: Calculation of torque on a rectangular coil, circular loop.

• ** Torque on a magnetic dipole in a magnetic field**:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Magnetic dipole moment, torque experienced by a magnetic dipole in a magnetic field, direction using the right-hand rule.

• Examples: Calculating the torque on a bar magnet in a magnetic field.

• ** Torque on a conducting rod in a magnetic field**:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Induced emf and current, Lorentz force, torque experienced by a conducting rod, direction using Fleming’s left-hand rule.

• Examples: Calculating the torque on a conducting rod moving perpendicular to a magnetic field.

4. Applications:

• Magnetic Levitation (maglev) Trains:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism.

• Key concepts: Principle of magnetic levitation, use of superconducting magnets, advantages, and limitations of maglev technology.

• Examples: Real-world maglev train systems.

• Electric Motors and Generators:

• References: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism.

• Key concepts: Basic principle of an electric motor and generator, role of magnetic fields, types of motors (DC and AC), Lenz’s law, induced emf, and back emf.

• Examples: Construction and working of simple DC motors and generators.

• Magnetic Resonance Imaging (MRI):

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Basic principle of MRI, use of strong magnetic fields and radio waves, generating 3D images, applications in medicine.

• Examples: MRI procedure and its medical significance.

• Magnetic Compasses:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Principle of magnetic compass, Earth’s magnetic field, magnetic declination, dip angle.

• Examples: Working and importance of magnetic compasses in navigation.

• Magnetic Separation:

• Reference: NCERT Class 11, Chapter - Motion in a plane

• Key concepts: Use of magnetic fields to separate magnetic materials from non-magnetic materials, applications in industries like mining, recycling, and food processing.

• Examples: Magnetic separation of iron ore from impurities.

5. Problem-Solving Techniques:

• Using vector analysis to calculate forces and torques:

• Reference: NCERT Class 11 and Class 12, Various chapters on vectors

• Key concepts: Components of vectors, vector addition, subtraction, and cross-product, applying vector analysis to magnetic force and torque calculations.

• Examples: Calculating the magnetic forces and torques acting on charged particles and current-carrying conductors using vector analysis.

• Applying Right Hand Rule for Forces and Torques:

• Reference: NCERT Class 12, Chapter - Magnetic Effects of Current and Magnetism

• Key concepts: Right-hand rule for determining the direction of magnetic force and torque, visualizing the directions using the thumb, fingers, and palm of the right hand.

• Examples: Applying right-hand rules in various problems involving force and torque calculations.

• Using superposition principle for magnetic fields:

• Reference: NCERT Class 11 and Class 12, Various chapters on vectors

• Key concepts: Superposition principle, calculating magnetic field due to multiple sources like current-carrying wires, solenoids, or bar magnets.

• Examples: Calculating the total magnetic field at a given point due to multiple magnetic sources.

• Solving numerical problems:

• Reference: NCERT Class 11 and Class 12, chapters related to electromagnetism

• Key concepts: Formula-based calculations involving force, torque, magnetic field, magnetic dipole moment, etc.

• Examples: Solving numerical problems on force exerted on moving charges, torque on current loops, magnetic field strength, and magnetic dipole interactions.