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# HR26 - Chapter 26 Current and Resistance In this chapter we...

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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 v d ) - Resistance (symbol R ) and resistivity (symbol ρ ) of a conductor -Ohmic and non-Ohmic conductors We will also cover the following topics: -Ohm’s law -Power in electric circuits J G (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 directi Electric current ons and thus there is no net charge transport. We now make a break in the conductor and insert a battery as shown in fig.b. Points A and B are now at potentials and , respectively. ( the A B A B V V V V V = voltage of the battery) The situation is not static any more but charges move inside the conductor so that there is a net charge flow in a particular direction. This net flow of electric charge we define as " " electric currrent A B (26 - 2)