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EMI and AC Class 12 [Complete Details] | JEE 2022 & NEET 2022 | Shreyas Sir | Vedantu Enlite

Vedantu JEE English・2 minutes read

The "Zero to Superhero" series focuses on electromagnetic induction and AC current, providing essential concepts for JEE and NEET aspirants through practical examples and live interaction to aid in exam preparation. The sessions cover topics like Faraday's law, Lenz's law, and inductors, emphasizing the importance of practice and active learning for score improvement in competitive exams.

Insights

  • The "Zero to Superhero" series on the VN Light channel offers a comprehensive revision of electromagnetic induction and AC current concepts, crucial for JEE and NEET exams, delivered by a physics master teacher at Vidantu.
  • Practical examples and detailed explanations provided during the sessions help students grasp complex topics like magnetic flux, Faraday's law, and inductors, enhancing their exam preparation.
  • The sessions cover a wide array of topics, from eddy currents and inductors to AC circuits and transformers, emphasizing the importance of structured study, active learning, and practice to improve exam scores significantly.

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Recent questions

  • What is the "Zero to Superhero" series about?

    The "Zero to Superhero" series is a revision series for JEE and NEET aspirants preparing for the 2022 exam. It focuses on electromagnetic induction and AC current, essential chapters for competitive exams. The instructor, a physics master teacher at Vidantu, provides a quick recap of important concepts through a mind map and handwritten notes. The session is conducted on the VN Light channel, catering to English medium students preparing for various exams. Viewers are encouraged to subscribe and like the channel for more sessions and updates.

  • How can I join the Telegram group for additional resources?

    A link in the description box of the session allows viewers to join a Telegram group for additional resources like PDFs. This group serves as a platform for students to access supplementary materials and engage with other learners to enhance their understanding of the concepts covered in the sessions. By clicking on the provided link, viewers can easily become part of the community and benefit from the shared resources.

  • What is the formula for calculating EMF in a rotating rod?

    For a rotating rod in a magnetic field, the EMF formula is B omega L^2 / 2, with the direction of the battery-like setup determining the current flow. This formula helps in determining the induced electromotive force when a rod rotates within a magnetic field. By understanding and applying this formula, students can grasp the concept of EMF generation in such scenarios and its implications in practical applications.

  • How are inductors different from resistors in circuits?

    Inductors resist changes in current, unlike opposing current directly. In circuits, inductors play a crucial role in opposing variations in current flow, storing energy in the form of a magnetic field. This characteristic distinguishes them from resistors, which directly impede the flow of current in a circuit. Understanding this disparity is essential for students to comprehend the behavior of inductors and their impact on circuit dynamics.

  • What is the significance of RMS value in AC circuits?

    The Root Mean Square (RMS) value is calculated by squaring all values, summing them, dividing by n, and taking the square root; it represents the constant current or voltage that generates the same heat as an AC current in a resistor. In AC circuits, the RMS value is crucial for determining the effective value of current or voltage, providing a standardized measure for comparison and analysis. By grasping the concept of RMS value, students can accurately assess the power and behavior of AC circuits in various applications.

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Summary

00:00

"JEE/NEET Revision: Electromagnetic Induction & AC"

  • The "Zero to Superhero" series is a revision series for JEE and NEET aspirants preparing for the 2022 exam.
  • The session focuses on electromagnetic induction and AC current, essential chapters for competitive exams.
  • The instructor, a physics master teacher at Vidantu, provides a quick recap of important concepts through a mind map and handwritten notes.
  • The session is conducted on the VN Light channel, catering to English medium students preparing for various exams.
  • Viewers are encouraged to subscribe and like the channel for more sessions and updates.
  • A link in the description box allows viewers to join a Telegram group for additional resources like PDFs.
  • A weekly quiz link is provided for timed assignments to practice concepts covered in the sessions.
  • The instructor interacts with viewers, addressing their comments and questions during the live session.
  • The session includes a revision of concepts like magnetic flux, Faraday's law, Lenz's law, and motional EMF.
  • Practical examples and explanations are given to help students understand the concepts better, aiding in exam preparation.

15:40

"EMF, Eddy Currents, and Inductors Explained"

  • Velocity parallel to magnetic field results in zero EMF due to the cross product being zero.
  • EMF is generated when a rod moves perpendicular to the magnetic field, with the formula being L dot (V cross B).
  • The direction of EMF is determined by the cross product of velocity and magnetic field.
  • For a rotating rod in a magnetic field, the EMF formula is B omega L^2 / 2, with the direction of the battery-like setup determining the current flow.
  • Curved wires can be replaced by straight wires to calculate EMF, with the length being twice the radius.
  • Eddy currents are induced when a conductor moves in a magnetic field, leading to heat loss due to kinetic energy conversion.
  • The energy for heat loss in eddy currents comes from an external force or the kinetic energy of the moving object.
  • Eddy currents can be utilized for braking in electric trains, where heat loss due to current loops helps in slowing down the train.
  • The concept of inductors is introduced, following discussions on eddy currents and motional EMF.
  • Lorentz force is relevant in scenarios where the force required to move an object with current in a magnetic field needs to be calculated.

31:33

Forces and Energy in Inductors and AC

  • Lorentz force is balanced by another force to maintain constant velocity.
  • The concept of ILB is linked with EMI or motional EMF.
  • Inductors are discussed before moving on to AC.
  • Inductors resist changes in current, unlike opposing current directly.
  • Inductors can be self-inductive or mutually inductive.
  • Self-inductance opposes changes in current within the same coil.
  • Mutual inductance involves two coils affecting each other's currents.
  • Energy stored in an inductor is calculated as half LI^2.
  • In LR charging, current gradually increases due to inductor resistance.
  • In LR discharging, energy stored in the inductor is dissipated as heat.

47:59

Understanding AC Circuits: RMS, Phasors, and Power

  • Galvanometer shows average voltage in a circuit; current in inductor is the same as the current in the circuit due to series connection.
  • Root Mean Square (RMS) value is calculated by squaring all values, summing them, dividing by n, and taking the square root; it represents the constant current or voltage that generates the same heat as an AC current in a resistor.
  • RMS value for a sine or cosine voltage is Vmax divided by root 2, and for current, it is Imax divided by root 2; root 2 value is 1.414 and 1 by root 2 value is 0.707.
  • Resistance is inherent in all components, even wires, so connecting a resistor is unnecessary; resistance represents the resistance of the battery, wires, and inductor coil.
  • AC voltmeters and ammeters are essential for measuring AC voltage and current, as conventional ammeters based on deflection do not work; hot wire instruments measure heat to determine voltage or current.
  • Phase indicates synchronization between components; time domain graphs show values at specific times, while phase domain graphs show synchronization between current and voltage.
  • Phasor diagrams represent circular motion whose shadow is an oscillation; phasors help understand circuits and add/subtract quantities, indicating phase differences between current and voltage.
  • In LCR circuits connected to an AC source, all components are in series, sharing the same current but not the same voltage due to vector addition; phasor diagrams aid in understanding the phase differences between components.
  • Voltage across a resistor is in phase with the current, while voltage across an inductor leads the current and voltage across a capacitor lags the current by 90 degrees.
  • Power loss in DC circuits is calculated as I squared R, while in AC circuits, it is I RMS squared R; power factor, represented by cos phi, indicates the phase difference between voltage and current.

01:05:23

"Phasor Diagram: Voltage Relationships in Circuits"

  • Phasor diagram shows resistor, inductor, and capacitor voltages moving together.
  • Voltage across resistor is in tandem with current.
  • Vector addition of resistor, inductor, and capacitor voltages gives total voltage E0.
  • VL and VC, being opposite, are first considered in vector addition.
  • VR remains as is, with the addition of VL and VC diagonally.
  • Net EMF is found using Pythagoras theorem.
  • Phase difference exists between net EMF and current.
  • Inductor and capacitor have reactances, not resistances.
  • Reactance is named so due to energy storage properties.
  • Impedance is total resistance plus reactance in the circuit.

01:22:32

"Transformers, Inductors, and Mutual Inductance Explained"

  • Step up transformer increases voltage, step down transformer decreases voltage.
  • Transformers involve theory, construction materials, and lamination.
  • Isolation transformer has equal input and output currents, isolating circuits.
  • Emf is del phi by del t, current is emf by resistance, and charge is emf by resistance.
  • Power in a coil after closing a switch is pi r square b naught.
  • Moving a bar magnet along a coil axis induces current in opposite directions.
  • Emf in a coil with a short bar magnet moving along its axis is b naught e to the power -t.
  • Emf in a coil with a square coil rotating in a field is 10 to the power -2 teslas.
  • Inductor delays current decrease, resistor instantly stops current.
  • Mutual inductance between two coils is 0.1 henry.

01:39:47

"Transformers, Exams, and Resonant Circuits Explained"

  • Difficulty level on YouTube in 2020 varied from easy to hard due to numerous content creators.
  • Completing one chapter typically took two weeks, but advice was given to speed up the process.
  • Primary and secondary coils for transformers had 50 and 1500 turns respectively.
  • The magnetic flux in the primary coil was specified, along with the time in seconds.
  • Advice was given to prepare for exams in 2022 or 2023, emphasizing a structured study approach.
  • To find the primary voltage in a transformer, Faraday's law was applied.
  • The primary voltage was calculated to be 4 volts, leading to a secondary voltage of 120 volts.
  • The process of finding the root mean square (RMS) value for a given graph was explained.
  • The concept of RMS value was demonstrated through a detailed calculation involving resistors and current flow.
  • A series resonant circuit involving LCR components was analyzed to determine the voltage across the inductor at resonance.

01:57:32

"Practice and active learning boost scores"

  • Improvement in scores by 100 points is achievable through practice, learning from mistakes, and testing oneself, rather than just watching videos; emphasizing the importance of practice over passive learning, suggesting the use of mind maps for effective revision.
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