# physics

a conductor is 2m long and 8mm diameter if its resistivity is 1.8*10^-8 ohmm calculate
a,the resistance of the conductor
b,the current in the conductor when a p.d of 10v is maintained across its ends
c,the current density
d,the electric field in the wire

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1. L=2 m,
s=πr² = π(8*10⁻³)² =64π*10⁻⁶ m²,
ρ=1.8*10⁻⁸Ohm•m.
a. R= ρL/s
b. I=U/R
c. j=I/s
d. the charges are on the surface
of the wire => the electric in the wire is zero

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