Induction - An Introduction: Crash Course Physics #34

CrashCourse
16 Dec 201609:49
EducationalLearning
32 Likes 10 Comments

TLDRThis episode of Crash Course Physics explains how physicists in the 19th century discovered that changing magnetic fields can induce electric currents. Joseph Henry and Michael Faraday showed that while constant magnetic fields do not create currents, changing magnetic fields do through the concept of magnetic flux. The induced current flows in a direction that opposes the change in magnetic flux, as described by Lenz's law. The episode further explains how to calculate the induced emf and apply these principles to understand hard drives. Overall, it provides a foundational explanation of induction and its applications.

Takeaways
  • 😲 Magnetic fields can induce electric currents, but only when the magnetic field is changing over time
  • 😃 Faraday discovered that changing magnetic fields over time induce electric currents in nearby conductors
  • 📏 The key property that determines induced EMF is magnetic flux - the magnetic field passing through a surface
  • 📈 Changes in magnetic flux over time induce an EMF, creating a current
  • 🤓 There are 3 factors that affect magnetic flux: magnetic field strength, conductor area, conductor angle
  • 🔀 Lenz's law states that the induced current will create a magnetic field that opposes the change causing it
  • ✅ You can use the right hand rule to determine the direction of the induced current
  • 🖥 Hard drives store data by magnetizing sections of a rotating disk, then reading the data via electromagnetic induction
  • 🤯 Moving a conductor in and out of a magnetic field also induces a current, with EMF proportional to velocity
  • 💡 Induced currents are useful for generators, transformers, motors, hard drives, and more
Q & A

  • What did physicists discover about electric currents and magnetic fields in the 19th century?

    -Physicists discovered that electric currents can create magnetic fields.

  • What did scientists wonder after discovering that electric currents can create magnetic fields?

    -Scientists wondered if the opposite was also true - if magnetic fields could create or induce electric currents.

  • Why did early experiments trying to detect electric currents induced by magnetic fields keep failing?

    -The early experiments kept failing because the magnetic fields were not changing over time. Only a changing magnetic field induces an electric current.

  • What is Faraday's Law of Induction?

    -Faraday's Law of Induction states that a changing magnetic field will induce an electromotive force (EMF) in a loop of wire.

  • What three factors affect the magnetic flux through a loop of wire?

    -The three factors that affect magnetic flux through a loop are: the strength of the magnetic field (B), the area of the loop (A), and the angle (theta) between the magnetic field and a line perpendicular to the loop.

  • How is the direction of the induced electric current determined?

    -Lenz's Law states that the induced current will generate a magnetic field to oppose the change in original magnetic flux. Using the right-hand rule on this opposing magnetic field gives the direction of the induced current.

  • How is an EMF induced when moving a loop of wire in and out of a magnetic field?

    -The induced EMF is equal to the magnetic field strength times the length of the wire loop times the velocity of the loop.

  • How do hard drives use magnetic induction?

    -Hard drives magnetize small sections of a rotating disk to store data. As the disk rotates, the changing magnetic fields induce currents in an electromagnet coil, which is processed as computer data.

  • What happens when magnetic flux through a coil changes?

    -A changing magnetic flux will induce an EMF in the coil. The total EMF depends on the number of loops in the coil.

  • What causes a current to be induced in a loop of wire?

    -A changing magnetic field through the loop causes induction. Specifically, it is the change in magnetic flux over time that induces the EMF and current.

Outlines
00:00
⚡️ Faraday's Law of Induction

This paragraph provides an overview of Faraday's experiments with electromagnetism. It explains that a constant magnetic field does not induce electric current in a wire loop, but a changing magnetic field does. The induced EMF is proportional to how quickly the magnetic field changes over time. Magnetic flux, which measures the magnetic field through a wire loop, is a key concept. The factors that influence magnetic flux are explained.

05:02
😀 Applying Lenz's Law

This paragraph explains Lenz's law and how to apply it to determine the direction of induced current. Using the example scenarios of moving a bar magnet toward or away from a wire loop, it demonstrates how to analyze the direction of the induced magnetic field. By applying the right-hand rule, the direction of the resulting current can then be determined.

Mindmap
Keywords
💡electric current
Electric current refers to the flow of electric charge carriers. It is a key concept in the video, which discusses how magnetic fields can induce electric currents. Joseph Henry and Michael Faraday discovered that changing magnetic fields over time can create electric currents in nearby conductors. This led to various technologies like hard drives.
💡magnetic field
Magnetic field refers to the magnetic influence in a region surrounding magnets or electric currents. The video focuses on how changing magnetic fields interact with conductors to induce electric currents, as described by Faraday's Law of Induction. For example, rotating hard drive disks through an electromagnet's magnetic field induces currents used to read data.
💡electromotive force (EMF)
Electromotive force refers to the electrical force that causes charges to move through a conductor. In Faraday's experiments, changing magnetic flux induced an EMF in coils, pushing charges to form electric currents. Lenz's law describes the direction of these EMF-induced currents.
💡magnetic flux
Magnetic flux measures the quantity of magnetic field passing through a surface like a wire loop. Faraday discovered currents are induced when magnetic flux through a coil changes over time. It depends on the field strength, loop area, and their relative angle.
💡Faraday's Law
Faraday's Law of Induction states that changing magnetic flux through a coil induces an electromotive force and current within it. This key discovery showed magnetic fields can produce electric currents under certain conditions, enabling technologies from generators to hard drives.
💡Lenz's Law
Lenz's law describes the direction of currents induced by electromagnetic forces based on opposing field changes. For example, if a magnet moves towards a coil, increasing the flux, the induced current creates a field against this change.
💡electromagnet
An electromagnet consists of a coil of wire that creates a magnetic field when electric current flows through it. Hard drive heads contain electromagnets to read data via electromagnetic induction from the rotating disk changing the magnetic flux through the coils.
💡generator
A generator converts mechanical energy into electrical energy using electromagnetic induction - for example, by rotating coils within magnetic fields. The discovery of induction enables generator technologies from hydroelectric dams to bicycle dynamos.
💡hard drive
Hard drives store data by magnetizing rotating disks, then use induction to generate currents in an electromagnet head as sections spin through its field, detecting the magnetized zones. This demonstrates a key application of Faraday's induction discoveries.
💡induction
Electromagnetic induction refers to the production of electric currents in conductors exposed to changing magnetic fields. This phenomenon, described by Faraday's Law, enables technologies from medical devices to wireless chargers to read computer data.
Highlights

First significant research finding

Introduction of new theoretical model

Proposed innovative methodology for analysis

Key practical application and recommendations

Transcripts

Browse More Related Video

michael faraday | law of electromagnetic induction | faraday's law of induction

10. Ampere's Law

Lenz's Law, Right Hand Rule, Induced Current, Electromagnetic Induction - Physics

Magnetic (AP Physics SuperCram Review)

Faraday's Law of Electromagnetic Induction, Magnetic Flux & Induced EMF - Physics & Electromagnetism

Maxwell's Equations: Crash Course Physics #37

Rate This

5.0 / 5 (0 votes)

Thanks for rating: