Question

71. A student makes a homemade resistor from a graphite pencil 5.00 cm long, where the graphite is 0.05 mm in diameter. The resistivity of the graphite is 5 ρ 1.38 10 / m − = ×Ω . The homemade resistor is place in series with a switch, a 10.00-mF capacitor and a 0.50-V power source. (a) What is the RC time constant of the circuit? (b) What is the potential drop across the pencil 1.00 s after the switch is closed?

Answer 1

Usiy His fesmula Criven, g138 X10-5 0.05 X10"3 m 2

-IS 3-52s V4-55V