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Plus Two Physics | Chapter 4 | Moving Charges and Magnetism | Oneshot | Exam Winner Plus Two

Exam Winner Plus Two・2 minutes read

The live Physics class emphasizes moving charges and magnetism, with a detailed focus on force, direction, and equations involving velocity and magnetic fields. The Back Lock series offers free revision sessions for students, aiding in achieving high scores in exams and includes detailed learning videos and question discussions for each chapter.

Insights

  • The live class focuses on the fourth chapter of Physics, emphasizing moving charges and magnetism, with a deadline set for completion before September.
  • The Back Lock series offers free revision sessions, short notes, live classes, and question discussions for students struggling with certain chapters, aiming to aid in achieving a 95% score in public exams.
  • Magnetic force is perpendicular to velocity, resulting in zero work done, and the direction is determined by the Fleming's Left Hand Rule.
  • Ampere's Law is utilized to find magnetic fields around current-carrying wires, with the magnetic field inside a solenoid being uniform and constant.
  • The concept of torque is crucial, calculated by multiplying ILB by the perpendicular distance, with the formula M * B * sin(theta) representing the magnetic moment's role in determining torque.

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Recent questions

  • What is the relationship between magnetic field and moving charges?

    The magnetic field surrounds a charge and exerts force on it, causing movement. The force is applied to a charge by the magnetic field, with the magnetic force equation involving the charge, velocity, and magnetic field. The direction of the force is determined by Fleming's Left Hand Rule, and it is always perpendicular to both velocity and the magnetic field. This force is characteristic in that it is always perpendicular to velocity, resulting in zero work done. The magnetic force is exerted when the velocity is perpendicular to the magnetic field, resulting in zero force when parallel or anti-parallel.

  • How is circular motion influenced by magnetic fields?

    Circular motion in a magnetic field occurs when the velocity of a charge is perpendicular to the magnetic field, resulting in a circular path due to the centripetal force provided by the magnetic force. The centripetal force equation involves the magnetic force providing the necessary centripetal force, with the radius calculated using the charge's mass, velocity, and magnetic field strength. The time period of rotation is the time taken for a charge to complete a full circle in a magnetic field, influenced by the strength of the magnetic field and the velocity of the charge. Different motions can occur based on the angle between velocity and the magnetic field, leading to various path shapes and characteristics.

  • How is magnetic force experienced by current-carrying wires calculated?

    The force experienced by a current-carrying wire in a magnetic field is determined by the formula QVBsineθ, where Q represents the charge, V is the velocity of the charge, B is the magnetic field strength, and θ is the angle between the velocity and the magnetic field. The drift velocity of electrons in the wire is calculated using the formula V = ILB sine θ, where I is the current, L is the length of the wire, and B is the magnetic field strength. The direction of the force is determined by Fleming's Left Hand Rule, with the magnetic field being inward and the current being downward. The total force experienced by electrons in the wire is calculated by multiplying the force experienced by one electron by the total number of electrons in the wire.

  • What are the key concepts related to Ampere's Law and magnetic fields?

    Ampere's Law is employed to find magnetic fields around current-carrying wires, with the line integral of the magnetic field around any closed loop being equal to the total current passing through it. The magnetic field due to a straight wire is calculated using Ampere's Law and the equation Mu Zero i/2πr, with the field being tangential and inward or outward depending on the point. Inside a solenoid, the magnetic field is uniform and constant, while it is negligible outside. The magnetic field equation inside the solenoid is derived using Ampere's Law and a rectangular Amperian loop, with specific calculations for each segment of the loop. The magnetic field inside a toroid is explained to be zero, with the exterior loop's magnetic field determined using the Ampere's Law integral considering the current flowing through the toroid.

  • How is torque calculated in the context of magnetism?

    Torque in the context of magnetism is calculated by multiplying the current, length, and magnetic field strength by the perpendicular distance. The formula for torque involves ILB multiplied by the perpendicular distance, emphasizing the importance of current, area, and magnetic moment in determining torque. The torque experienced by a magnetic dipole in an electric field is determined by the number of turns, current, area, magnetic field strength, and angle. The discussion transitions to the torque experienced by a galvanometer, detailing its components like a soft iron core, rectangular coils, magnets, and a spring, and explaining how current passing through the coil causes deflection and torque.

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Summary

00:00

Physics Live Class: Moving Charges & Magnetism

  • The text introduces a live class on the fourth chapter of Physics, focusing on moving charges and magnetism.
  • The chapter is emphasized as crucial for preparation, with a deadline set for completion before September.
  • The live class aims to provide a comprehensive understanding of the chapter, urging students to participate actively.
  • The chapter is noted for its intensity, with an estimated duration of over two hours due to derivations.
  • A Back Lock series is introduced for students struggling with certain chapters, offering free revision sessions.
  • The Back Lock series includes short notes, live classes, and question discussions for each chapter.
  • The series aims to aid students in achieving a 95% score in public exams by providing detailed learning videos.
  • The text also announces a Pre-NEET exam for students preparing for the NEET exam, offering valuable practice and ranking opportunities.
  • Registration details for the Pre-NEET exam are provided, with a registration fee of ₹100 and instructions to access the registration link.
  • The text concludes by encouraging students to share the live class with friends and emphasizes the importance of thorough preparation for exams.

12:20

Magnetic Force on Moving Charges Explained

  • Magnetic field surrounds a charge, exerting force on it.
  • Force is applied on a charge by the magnetic field, causing movement.
  • The magnetic field gives force to a moving charge, not to a stationary one.
  • The magnetic force equation is Q x V x B, involving velocity and magnetic field.
  • The direction of the force is determined by the Fleming's Left Hand Rule.
  • The direction of the force is perpendicular to both velocity and magnetic field.
  • The force on a proton in an outward magnetic field is upward.
  • The force on an electron in an inward magnetic field is downward.
  • Work done by a uniform magnetic field on a charge entering it is calculated using force x displacement.
  • The magnetic force is always perpendicular to velocity, resulting in a dot product of zero.

25:30

Magnetic Force and Circular Motion Dynamics

  • Magnetic force characteristic: Always perpendicular to velocity, resulting in zero work done.
  • Magnetic force and velocity relationship: Force exerted when velocity is perpendicular to magnetic field, resulting in zero force when parallel or anti-parallel.
  • Lawrence Force concept: Total force experienced by a moving charge in the presence of both electric and magnetic fields.
  • Calculation of total force: Sum of electric and magnetic forces acting on a charge moving in both fields.
  • Special cases of force calculation: Force is zero when velocity is zero or parallel to magnetic field, maximum force at 90 degrees angle, and direction determined by left-hand rule.
  • Circular motion in magnetic field: Velocity perpendicular to magnetic field results in circular path due to centripetal force provided by magnetic force.
  • Centripetal force equation: Magnetic force provides centripetal force in circular motion, with radius calculated as MV/QB.
  • Time period of rotation: Time taken for a charge to complete a full circle in a magnetic field, influenced by magnetic field strength and velocity.

39:30

Understanding Distance, Speed, and Time in Motion

  • Understanding distance by time and time as a fundamental concept
  • Explaining distance by speed as distance covered in a time period
  • Formula for distance covered in a time period: 2πr
  • Relationship between distance, speed, and time period
  • Equation for time period: t = 2πm/qb
  • Impact of velocity on time period in circular motion
  • Different motions based on velocity and magnetic field angles
  • Derivation of helical path and pitch in circular motion
  • Concept of current flow in copper wire connected to a battery
  • Magnetic force on a current-carrying wire in a magnetic field formula: QVBsineθ

53:25

Electron Velocity in Magnetic Field Formula

  • Velocity V is the charge E of the electron
  • The magnetic field is represented by B sine theta
  • The general case is derived in a figure, showing the electron in a magnetic field at 90 degrees
  • The formula to use is for any angle, not just sine 90
  • The total force experienced by electrons is calculated by multiplying the force experienced by one electron by the total number of electrons
  • The number density of electrons in a wire is determined by dividing the total number of electrons by the volume of the wire
  • The volume of a cylindrical wire is calculated by multiplying the base area by the length of the wire
  • The drift velocity of electrons is calculated using the formula V = ILB sine theta
  • The force experienced by a current in a wire due to a magnetic field is given by the equation ILB sine theta
  • The direction of the force is determined using Fleming's Left Hand Rule, with the magnetic field being inward and the current downward

01:07:02

Charges, Fields, and Laws in Physics

  • The first chapter focuses on understanding how charges produce an electric field.
  • An electric field is created by charges, even though it is invisible.
  • Electric field lines are imaginary but represent the real electric field created by charges.
  • To create an electric field, charges do not need to move; stationary charges can suffice.
  • Charges that create an electric field can also create a magnetic field.
  • A moving charge, or current, generates a magnetic field around it.
  • The direction of magnetic field lines around a current-carrying wire can be determined using the right-hand rule.
  • The shape of magnetic field lines around a current-carrying wire or solenoid is circular.
  • Gauss's Law is used to detect electric fields around charged bodies.
  • Ampere's Law is employed to find magnetic fields around current-carrying wires.

01:20:21

Ampere's Law and Magnetic Field Analysis

  • The first step involves considering an imaginary Gaussian surface with a Gaussian Magnetic field at the surface.
  • A loop is taken, not a 3D surface, and it can be a circular loop or a loop with a different shape.
  • The loop is named Amperian loop, and the equation used is similar to a closed integral equation.
  • The equation involves the magnetic field written as B, with the length vector DL instead of the area vector DS.
  • The equation includes constants like Epsilon Zero and Mu Zero, representing the magnetic permeability.
  • Ampere's Law states that the line integral of the magnetic field around any closed loop is equal to the total current passing through it.
  • The magnetic field due to a straight wire is calculated using Ampere's Law and the equation Mu Zero i/2πr.
  • The magnetic field is circular at each point, with the magnetic field being tangential and inward or outward depending on the point.
  • The magnetic field is uniform and constant inside a solenoid, while it is negligible outside.
  • The magnetic field equation inside the solenoid is derived using Ampere's Law and a rectangular Amperian loop.

01:34:58

Calculating Magnetic Fields Using Amperian Loops

  • The process involves dividing the Amperian loop into segments AB, BC, CD, and DA, with specific equations for each segment.
  • The equation for calculating the magnetic field involves dot products and segment lengths, with specific steps for each segment.
  • The angle between the magnetic field and the segments plays a crucial role in determining the magnetic field's direction and magnitude.
  • The magnetic field is calculated based on the number of turns, current, and length of the solenoid, using the formula mu zero times the product of the number of turns and current divided by the length.
  • The total current in the solenoid is determined by multiplying the number of turns by the current in each turn.
  • The magnetic field inside a solenoid is calculated using the formula mu zero times the product of the number of turns and current divided by the length.
  • The concept of a toroid is introduced, with details on its structure and the calculation of the magnetic field inside and outside the toroid.
  • The Amperian loop method is applied to the toroid, with separate considerations for the interior and exterior loops.
  • The magnetic field inside the toroid is found to be zero due to the absence of current in the interior loop.
  • The exterior loop's magnetic field is determined using the Ampere's law integral, considering the current flowing through the toroid.

01:50:38

Loop Currents and Magnetic Fields Explained

  • B dot dl = mu zero i is the equation discussed
  • The importance of keeping children in the loop due to current inside it is highlighted
  • The concept of net current inside a loop is questioned
  • The direction of current flow inside a loop is explained
  • The significance of positive and negative currents in the loop is discussed
  • The net current inside the loop is determined to be zero due to equal current going in and out
  • The magnetic field inside a toroid is explained to be zero
  • The equation for the magnetic field inside a toroid is derived as B = mu zero n i / 2πr
  • The average length of a toroid is calculated as 2πr
  • The similarity between the magnetic fields of a solenoid and a toroid is emphasized

02:19:31

Award request leads to exam; Eq program ends.

  • Asking for the award is followed by asking for the exam.
  • Four points written as an Eq program signify the end of a chapter.
  • The chapter disliked due to excessive derivations.
  • The Biotz Award loan equation is crucial for derivations.
  • The equation involves a circular current-carrying wire.
  • The magnetic field around the wire is determined by the equation.
  • The angle between current elements and distances is significant.
  • Components of the magnetic field are divided into vertical and horizontal.
  • Vertical components cancel out, leaving only horizontal components.
  • The final derivation simplifies the magnetic field equation.

02:33:50

Magnetic Field Equations and Forces in Loops

  • The diagram for the exam should depict the subject matter, one's identity, and what is being taken.
  • Small R can be included in the diagram, and understanding its significance is crucial.
  • Derivation is highly important, especially for exam questions related to the magnetic field at the center of a current-carrying loop.
  • The equation for the magnetic field at the center involves specific calculations and placements.
  • Understanding the concept of magnetic dipole and its relation to current-carrying loops is essential.
  • The magnetic moment equation involves the current in a loop and its area vector.
  • The force on a rectangular current-carrying loop in a magnetic field is determined by the current, length, and angle.
  • The net force on a rectangular loop is zero due to the cancellation of forces in opposite directions.
  • The absence of torque in a current-carrying loop indicates that it will not rotate.
  • The torque produced by forces on different sides of the loop creates a couple, influencing the rotation of the loop.

02:49:10

Understanding Torque in Magnetism and Galvanometers

  • The first chapter discusses the concept of force, perpendicular distance, and magnetism, emphasizing the calculation of torque by multiplying ILB by the perpendicular distance.
  • The text delves into the derivation of torque, highlighting the importance of understanding the formula ILB * B * sin(theta) and the area of a rectangle in calculating torque.
  • It explains the significance of current, area, and magnetic moment in determining torque, stressing the formula M * B * sin(theta) and the cross product representation of torque.
  • The discussion transitions to the torque experienced by a magnetic dipole in an electric field, emphasizing the formula N * I * A * B * sin(theta) for multiple turns.
  • The final section introduces the working principle of a galvanometer, detailing its components like a soft iron core, rectangular coils, magnets, and a spring, and explaining how current passing through the coil causes deflection and torque.
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