- #1
MathematicalPhysicist
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i don't quite understand the derivation of mutual electrostatic energy of two charged system:
[tex]U_12=\frac{1}{4\pi}\intE_1(dot)E_2dV=-\frac{1}{4\pi}\intE_1(dot)\nebla\phi_2 dV= \frac{1}{4\pi}\int \phi_2(dot)\nebla(dot)E_1=\int \phi_2*\rho_1dV[/tex]
i undersantd that we are using here: [tex] (1)=\nebla(\phiE)=E(dot)\nebla\phi+\phi*\nebla(dot)E[/tex]
but why then (1)=0 here?
thanks.
[tex]U_12=\frac{1}{4\pi}\intE_1(dot)E_2dV=-\frac{1}{4\pi}\intE_1(dot)\nebla\phi_2 dV= \frac{1}{4\pi}\int \phi_2(dot)\nebla(dot)E_1=\int \phi_2*\rho_1dV[/tex]
i undersantd that we are using here: [tex] (1)=\nebla(\phiE)=E(dot)\nebla\phi+\phi*\nebla(dot)E[/tex]
but why then (1)=0 here?
thanks.