Eddy Current

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This video provides a detailed explanation of eddy currents (0:00). The speaker introduces eddy currents by giving the example of an induction cooktop (0:15), explaining how it heats food using a special utensil, unlike regular cooking methods (0:45).

Here's a breakdown of the key concepts discussed:

What are Eddy Currents?
When the magnetic flux linked with a metallic plate changes, the plate develops a current to oppose this change (1:28).
This opposition causes the free electrons in the metal to start a swirling motion, called "swirling of electrons" (2:51).
The current generated due to this swirling motion is known as eddy current (3:12).
The primary effect of eddy currents is heating (3:32).
Uses of Eddy Currents:
Induction Cooktops: They produce a time-varying magnetic field (4:06), which induces eddy currents in special cooking utensils (4:27), leading to heating (5:09). The copper coating at the bottom of these utensils increases the density of free electrons (4:40).
Electromagnetic Furnaces: Used to melt metals with very high melting points that cannot be melted by conventional fuels (5:21). A time-varying magnetic field is applied to induce eddy currents, generating immense heat (6:05).
Electromagnetic Brakes: Utilized in fast-moving trains like metros and bullet trains (7:32). Eddy currents are produced in the brake shoes, leading to increased heat and temperature, causing expansion and stopping the train (7:43).

Disadvantages of Eddy Currents:
The main disadvantage is energy loss due to heating in the core of electromagnetic devices like transformers (8:09).
To mitigate this, transformer cores are made of laminated, thin, insulated slices (8:58). This lamination reduces the space for electrons to swirl, thereby minimizing both copper loss and eddy current loss (9:05).

Mechanism of Electron Swirling:
The speaker clarifies that magnetic force does not directly cause the swirling of electrons at rest (10:09).
Instead, when the magnetic field changes, an electromagnetically induced electric field is produced (11:17). This induced electric field is responsible for initiating the swirling motion of the free electrons (11:31).
Notably, these induced electric field lines can form closed loops, unlike electrostatic field lines (12:03).