Assertion (A): When a resistance wire is stretched so as to make its length double, its resistance becomes 4 times of its original value. Reason (R ): Resistance of a conductor is directly proportional to its length and inversely proportional to its cross section area.

Assertion (A): When a resistance wire is stretched so as to make its l

1.	Assertion (A): When a resistance wire is stretched so as to make its length double, its resistance becomes 4 times of its original value. Reason (R ): Resistance of a conductor is directly proportional to its length and inversely proportional to its cross section area.
Answer» Both (A) and (R ) are true and (R ) is correct explanation of the assertion Both (A ) and ( R) are true but (R ) is not the correct explanation of the assertion. (A ) is true but (R ) is false (A) is false but (R ) is true Solution :When a resistance WIRE isstretched so as to make its length double it means that `L.=2l` How ever, as volume of wire must remain UNCHANGED, hence cross section AREA of wire is reduced to one half of its ORIGINAL value i.e., `A.=A/2` SO the new resistance `R.=(rho l.)/A.=(rho(2l))/((A//2))=4(rho l)/A=4R`.