Lemma in Electromagnetism

A particle of charge $q$ is projected in a radially symmetric axial magnetic field from its centre. Prove that the change in angular momentum about the centre when the particle is at a distance $r$ from the centre is given by: Where $ϕ$ is the flux through a circle of radius $r$ . Proof:

(Not my own)

This lemma can be used to solve Irodov 3.394 without writing messy differential equations :)

#ElectricityAndMagnetism

Easy Math Editor

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Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$