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CBSE NOTES CLASS 12 PHYSICS

CHAPTER 8 ELECTROMAGNETIC WAVES

Displacement current - the missing term in Ampere’s circuital law

Maxwell’s generalisation of Ampere’s circuital law

Maxwell equations

Source of electromagnetic waves

Maxwell’s theory of electromagnetic radiation

Why can’t we prove that light is an electromagnetic wave?

Nature of electromagnetic waves

Properties of electromagnetic waves

Speed of electromagnetic wave

Poynting vector

Energy in electromagnetic waves

Radiation pressure

Electromagnetic spectrum

Radio waves

Microwaves

CBSE NOTES CLASS 12 PHYSICS

CHAPTER 8 ELECTROMAGNETIC WAVES

Maxwell’s generalisation of Ampere’s circuital law

The source of a magnetic field is not just the conduction electric current, but also the time rate of change of electric field. Or the total current i is the sum of the conduction current denoted by ic, and the displacement current denoted by,

id=ɛodФEdt

That is,

i=ic+ id=ic+ ɛodФEdt 

The Amperes circuital law is modified as follows,

B.dl=μo i t

= μoic+ μoɛodФEdt

This is called Ampere Maxwell law.

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