Derive the law of conservation of charge from maxwell's equations. b express the electric field in terms of the scalar potential p and the vector potential a where b curl a. (note: for the general time-dependent case e is not equal to grad y alone.)

Deduce law of conservation of momentum from Newton's third law of motion. Consider two bodies A and B of masses mA and mB moving in the same direction along a straight line. ... Thus, total momentum of the two bodies is conserved provided no external force acts on them. This proves the law of conservation of momentum.

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