a] Define electric resistance of a conductor.
b] List the factors on which resistance of a conductor depends.
c] Resistance of a metal wire of length 1 m is `104Omega" at "20^(@)C`. If the diameter of the wire is 0.15 mm, find the resistivity of the metal at this temperature.

Explanation

a] Resistance is defined as the property of a conductor to resist the flow of charges through it. The resistance of conductor is numerically given as the ratio of potential difference across its length to the current flowing through it.
b] There are four factors that influence the resistance in a conductor.
Thickness [cross sectional area of the wire], length, temperature and resistivity of the material that is used. Some metals [copper, silver] have lower resistivity than others [iron, aluminum].
c] Resistance, `R=104Omega`
Length of wire, L = 1 m
Diameter of wire, d = 0.15 mm = `0.15xx10^(-3)m`
Cross-sectional area of wire, `A=pir^(2)=(pid^(2))/4" ""[becaused=2r]`
= `3.14xx((0.15xx10^(-3))^(2))/4=7.06xx10^(-8)m^(2)`
`R=(rhoL)/ArArrrho=(RA)/L=(26xx7.06xx10^(-8))/1`
`rho=1.8356xx10^(-6)Omegam`
Hence, resistivity is `1.8356xx10^(-6)Omegam" at "20^(@)C`