what is meant by electric resistance of conductor ? a wire of length L and resistance R is stretched so that its length is doubled and area of cross - section is halved .how will its a] resistance change b] resistivity change
what is meant by electric resistance of conductor ? a wire of length L and resistance R is stretched so that its length is doubled and area of cross - section is halved .how will its a] resistance change b] resistivity change
Resistance is a measure of the opposition that a circuit (or an electrical element) offers to the flow of electric current . You might compare it to the diameter of a hose. In fact, for metal wire, this is an excellent analogy: small-diameter wire has high resistance (a lot of opposition to current flow), and large-diameter wire has low resistance (not much opposition to electric currents). Resistance is measured in Ohms, Ω.
The dependence of resistance on length L and area of cross-section A of a wire is,
R = ρL/A
a)Resistance ‘R’ is related to length of the wire ‘L’, area of cross-section of the wire ‘A’ and resistivity ‘ρ’ as,
formula==> R = ρL/A
When Length is doubled
new length L'=2L
and area of cross-section is halved
new area of cross-section A'=A/2
then the new resistance is,
R ' = ρL'/A' = ρ(2L)/(A/2)=4ρL/A
=> R' = 4R
Thus, the resistance increases by 4 times.
change in resistance = resistance of the wire after stretching-resistance of the wire before stretching
=R'-R =4R-R
=3R
b)resistivity do not change on stretching it is a property of the material it remains constant for a particular material.it do not depend on length and area of conductor
Resistance is a measure of the opposition that a circuit (or an electrical element) offers to the flow of electric current . You might compare it to the diameter of a hose. In fact, for metal wire, this is an excellent analogy: small-diameter wire has high resistance (a lot of opposition to current flow), and large-diameter wire has low resistance (not much opposition to electric currents). Resistance is measured in Ohms, Ω.
The dependence of resistance on length L and area of cross-section A of a wire is,
R = ρL/A
a)Resistance ‘R’ is related to length of the wire ‘L’, area of cross-section of the wire ‘A’ and resistivity ‘ρ’ as,
formula==> R = ρL/A
When Length is doubled
new length L'=2L
and area of cross-section is halved
new area of cross-section A'=A/2
then the new resistance is,
R ' = ρL'/A' = ρ(2L)/(A/2)=4ρL/A
=> R' = 4R
Thus, the resistance increases by 4 times.
change in resistance = resistance of the wire after stretching-resistance of the wire before stretching
=R'-R =4R-R
=3R
b)resistivity do not change on stretching it is a property of the material it remains constant for a particular material.it do not depend on length and area of conductor
