A) derive from the definition of the clectric current i = [s df - j through the arca s the dwhere dq is the charge formula for the electric current inside a conducting wire i which flows through the cross section of the wire in the time dt stationary charge distribution, 2n wire have to be equal and independent of the cross sections of the wire both ends of the b) show that for a 0, the currents on oss c) given a stationary charge distribution. derive kirchhoff's current law, which states that the sum of all inflowing currents is equal to the sum of all out flowing currents d) show that a stationary field ē in a volume v performs the power p = jyj-edv. show that p ui holds for the case of a infinitesimal thin wire. hint: p where w q fre-dr