[問題] 用Delta函數表示電荷密度
如果有一根細棒子帶總電荷Q,長度R,直立於z軸 (也就是z=0到R)
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已知ρ(x) = a δ(θ) / r^2,求 a常數為何 (我知道δ(θ)表示θ=0時才會有電荷)
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我的想法是 ∫ρ(x)dv = Q
=> ∫∫∫(aδ(θ)/r^2) r^2sinθdrdθdψ = Q
=> 2πaR ∫δ(θ)sinθdθ = Q
到這邊就卡住了,∫δ(θ)sinθdθ不就是 sin0 = 0 嗎
還是我出發點有錯
我一直對Delta函數沒什麼概念
謝謝幫忙
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