Question

A copper wire 3 mm in diameter is wound about a cylinder whose length is 1.2 m and diameter 10 cm so as to cover the curved surface of the cylinder. Find the length of the wire used.

Answer 1

Curved surface area of cylinder $=2\pi rh=2\times \pi \times 5\times 12=120\pi c{m}^2$

$=120\pi c{m}^2$

Given width of wire $=0.3cm$

Area of wire $=l\times 0.3$

Acoording to the condition ;

$l\times 0.3=120\pi$

$\Rightarrow l=1256cm=12.56m$