8TH GRADE · ELECTROMAGNETIC INDUCTION
Electromagnetic induction and Lenz's rule
Magnetic flux, occurrence and direction of induction current.
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Basic Concepts
Electromagnetic induction
The appearance of an electric field and induced current when the magnetic flux through a circuit changes.
Current appears when the magnet moves relative to the coil, the current in an adjacent coil changes, or the circuit rotates.
Magnetic flux
A value characterizing the magnetic field passing through the selected surface.
The flux changes when the field, area, or orientation of the loop relative to the magnetic induction lines changes.
Lenz's rule
The induced current is directed so that its magnetic field counteracts the change in magnetic flux.
The rule expresses the conservation of energy: without external work, the system does not enhance the change that caused the current.
Physical quantities
Magnetic flux
A measure of the magnetic field passing through the surface of a loop.
Unit: weber ·
Contour area
The surface area bounded by a conductive circuit.
Unit: square meter ·
Lesson formulas
Magnetic flux
For a perpendicular uniform field, the flux is equal to the induction multiplied by the area of the circuit.
Condition: The field is uniform and perpendicular to the contour surface.
Tasks on the topic
Statements, answer options and the walkthrough.