The formulae we have derived earlier for series and parallel combinations
of resistors are not always sufficient to determine all the currents and
potential differences in the circuit Two rules, called Kirchhoff’s rules,
are very useful for analysis of electric circuits Given a circuit, we start by labelling currents in each resistor by a
symbol, say I, and a directed arrow to indicate that a current I flows
along the resistor in the direction indicated If ultimately I is determined
to be positive, the actual current in the resistor is in the direction of the
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