Why is partial derivative with respect to time used in the continuity equation,(adsbygoogle = window.adsbygoogle || []).push({});

[tex]

\frac{\partial \rho}{\partial t} = - \nabla \vec{j}

[/tex]

If this equation is really derived from the equation,

[tex]

\frac{dq}{dt} = - \int\int \vec{j} \cdot d\vec{a}

[/tex]

Then should it be a total derivative with respect to time?

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# Why partial derivatives in continuity equation?

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