Question

A wire of resistance R is stretched to twice of its original length and area decrease to half of its original value.its new resistance will be. a)4R b)R/9. c)3R. d)R/3​

Answer 1

Answer:

R=

A

pL

On, stretching a wire (a) volume of wire remains constant

(b) length of wire increases

(c) Area of cross section decreases

(d) Resistivity of wire = constant

On doubling length by stretching :

L

1

=2L

A

1

=A/2

∴R

1

=

A

1

pL

1

=

2

A

p(2L)

=

A

4pL

=4r