littlecat Group Title The surface charge density of an object is σ = dq/dA. Why is the total charge on the surface, Q = double integral σ dA ? 2 years ago 2 years ago

total charge on surface = surface charge density* area basically, surface charge density is the charge per unit area ...which means how much charge does an unit area has. so here $q=\int\limits_{0}^{A}dA*\sigma$
if charge density would have varied then we might have used $q= \int\limits_{0}^{A}dA* \sigma + \int\limits_{0}^{\sigma} d \sigma*A$