Physics: Current Electricity

Current Electricity Current density  Drift velocity  EMF of a cell E =  Terminal Pd of cell Terminal P.D. of cell when cell being discharged V = E - ir Terminal P.D. of cell during charging is V = E + ir Current in a circuit i =  Series Arrangement Total resistance of circuit = R + nr Current I =  Parallel Arrangement Net internal resistance =  Total resistance of circuit =  Current  Mixed Grouping Net internal resistance =  Net resistance of circuit =  Current  Ohm's law  Reciprocal of resistance is conductance G =  Specific resistance  Specific conductance  Variation of resistance with temperature R1 = R0 (1 + t) or  Comparision of resistance If 2 wires are made of different materials If 2 wires are made of same material  Resistance in series R = R1 + R2 + R3 If n wires each having resistance R' are connected in series, equivalent resistance R = nR' Resistance in parallel If 2 wires are connected in parallel R =  Kirchhoff's rule First rule  Wheatstone's Bridge Condition for balance is  The  bridge is most sensitive if P = Q = R = S Equivalent resistance of balanced bridge across the ends of battery =  If  and R =  VB = VD Potential gradient (X)