Chapter 26 Current and Resistance In this chapter we will introduce the following new concepts:-Electric current ( symbol i)-Electric current density vector (symbol )-Drift speed (symbol vd)-Resistance (symbol R)and resistivity (symbol ρ)of a conductor -Ohmic and non-Ohmicconductors We will also cover the following topics:-Ohm’s law -Power in electric circuits JG(26 - 1)
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Consider the conductor shown in fig.a. All the points inside the conductor and on its surface are at the same potential. The free electrons inside the conductor move at random directiElectric currentons and thus there is no net charge transport. We now make a break in the conductorand insert a battery as shown in fig.b.Points A and B are now at potentials and , respectively.( the ABABVVVVV−=voltage of the battery)The situation is not static any more butcharges move inside the conductor so thatthere is a net charge flow in a particulardirection. This net flow of electric chargewe define as ""electric currrentAB(26 - 2)