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a carbon resistor is 9 mm long and has a constant cross section of 0.3 mm2. the conductivity of carbon at room temperature is s = 3 multiplied by 104 per ohm·m. in a circuit its potential at one end of the resistor is 10 volts relative to ground, and at the other end the potential is 16 volts. a thin copper wire in the same circuit is 9 mm long and has a constant cross section of 0.3 mm2. the conductivity of copper at room temperature is s = 6 multiplied by 107 ohm-1m-1. the copper wire is in series with the carbon resistor in the same circuit mentioned above, with one end connected to the 16 volt end of the carbon resistor. calculate the resistance r of the copper wire and the potential vat end at the other end of the wire.
r =
vat end = v

you can see that for most purposes a thick copper wire in a circuit would have practically a uniform potential. this is because the small drift speed in a thick, high-conductivity copper wire requires only a very small electric field, and the integral of this very small field creates a very small potential difference along th