Question

How does the resistance of a wire change when: 

 its length is tripled? 

Answer 1

Resistance,  

`R=l/A`
 where l = length of  wire
            A= area of cross-section of the wire 

When the length is tripled, l' = 3l

New resistance, 

`R'=l/A ` 

`R'=(rho(3l))/A=(3l)/A` 

`R=3R` 

`R=P/A` 

Thus, the resistance will become three times the original resistance.