Question

A wire of length l and area of cross section A has a resistance 20 ohm what will be new resistance and the resistivity of the wire if it is stretched to double its original length

Answer 1

Explanation:

1. Resistivity is a property of the material hence will not change.
2. Resistance will become twice (40 Ohm) if the length is doubled without changing its cross sectional area

Answer 2

Answer:

resistance will be 80 ohms and resistivity will be the same.

Explanation:

resistance depends on

1) nature

2)temperature

3) length of conductor

4) area of cross section of conductor

We know that,  

RαL

and Rα  A/1

​  

If the L length of wire is stretched to 1L length then its Area of cross section.

becomes half, i.e., =  A/2

 

We know that, R=  ρL/A

​  

 

Where ρ is known as resistivity of an conductor.

On putting values, R=  ρ2L / A/2

                                     

​  

 

R=4  pL/A

​

resistance becomes 4 times

Resistivity only depends on the characteristic nature of the conductor and does not change