Answer:
The percentage change in resistance of the wire is 69%.
Explanation:
Resistance of a wire can be determined by,
R = (ρl) ÷ A
Where R is its resistance, l is the length of the wire, A its cross sectional area and ρ its resistivity.
When the wire is stretched, its length and area changes but its volume and resistivity remains constant.
= 1.3l, and
=
So that;
= (ρ
) ÷
= (ρ × 1.3l) ÷ (
)
= (1.3lρ) ÷ ()
= × [(ρl) ÷ A]
= 1.69R (∵ R = (ρl) ÷ A)
= 1.69R
Where is the new resistance,
is the new length, and
is the new area after stretching the wire.
The change in resistance of the wire = - R
= 1.69R - 1R
= 0.69R
The percentage change in resistance = × 100
= 0.69 × 100
= 69%
The percentage change in resistance of the wire is 69%.