List two distinguishing features between the resistance and resistivity of a conductor. A wire is stretched so that its length becomes 6/5 times of its original length. if its original resistance is 25 W, find its new resistance and resistivity .Give justification for your answer in each case.?

Question

Answer

Distinguishing features between Resistance and Resistivity

Resistance:
- Resistance is the measure of a material's opposition to current flow.
- It depends on the length, cross-sectional area, and temperature of the conductor.

Resistivity:
- Resistivity is the measure of a material's resistance per unit length and area.
- It is an intrinsic property of the material and depends only on its chemical composition.

Calculation of New Resistance and Resistivity

Given:
- Original length of wire = L
- Stretched length of wire = 6/5L
- Original resistance of wire = 25 W

To find:
- New resistance of wire
- New resistivity of wire

Formula:
- Resistance = Resistivity x Length / Cross-sectional area

Calculation:
- Cross-sectional area remains the same as the wire is stretched uniformly.
- New length of wire = 6/5L
- Using the formula of resistance, R = ρL/A
- New resistance = ρ*(6/5L)/A
- New resistance = (6/5)ρL/A = (6/5)*25 W = 30 W
- Using the formula of resistivity, ρ = RA/L
- New resistivity = (30 W)*(L/(6/5)L) = 25 W*(5/6) = 20.83 Wm

Justification:
- The new resistance increases because the length of the wire increases while its cross-sectional area remains the same.
- The new resistivity decreases because the length of the wire increases while its resistance increases.

Answer

Resistivity is the resistance offered by that material of length 1m and area of cross section 1metre square.
resistivity=RA÷l (R=resistance
A=area of cross section
l=length)

Resistance is the property of the wire to oppose the electric current.
resistance=V÷I(V=Volt,I=current)

Answer

Features of resistance:-
1. it is the obstruction offered in flow of current by wire.
2. it depends on material of wire ,temperature, area of cross sectionand length of wire.
features of resistivity:-
1.it is the tendency of a substance to offer obstruction in flow of curent per unit area .
2. it depends onlo on material of wire.

Resistance of a conductor of length L and an area of uniform cross section is
R = ρ L / A , ρ = resistivity of the material
given R = 25 Ω

Volume of the material in the conductor = L A.
Let us assume that the density of the material remains the same. Hence the volume Vol of the conductor remains the same.

Vol = A L = A' L' => A' = A L / L'

After stretching the wire : L' = 6 L / 5

A' = 5 A L / 6 L = 5 A / 6

Resistance of stretched wire = R' = ρ L' / A' = ρ ( 6 L /5) * [ 6 / (5 A) ]

R' = 36 ρ L / (25 A) = 36 R / 25

New resistance = 36 * 25 / 25 Ω = 36 Ω

Answer

New reistance is 36 ohm and resistivity will be same no change in resistivity
Note =
if there are the CAse of streching wire or in case of volume constant..
R1/R2= L12/L22
in case of Area
R1/R2= A22/A12

and resistivity no change being same material ..

Answer

Resistance-V=IR
resistivity-R=pl\A
si unit of resistance is ohm
si unit of resistivity is ohm meter
in resistance current is constant
in resistivity rho is constant

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