Given:
A copper rod of diameter 1 cm and length 8 cm is drawn into a wire of length 18 m of uniform thickness.
To find :
the thickness of the wire.
Solution:
Diameter of copper wire =1 cm
Radius = \(\frac{1}2\)cm
Height of copper rod =Length of copper rod = 8 cm
Volume of rod = πr2h
= \(π\times(\frac{1}{2})^2\times8\)
Let the radius of wire be ‘r’ cm
As
1 m = 100 cm
length of the wire=Height of the wire = 18 m =1800 cm As rod is converted into wire,Therefore,
Volume of cylinder wire = Volume of cylindrical rod
⇒ r = 0.033 cm
Hence thickness of the wire is 0.033 cm.
⇒ πr2 x 0.18
\(π\times(\frac{1}{2})^2\times8\)
⇒ r2 = 
⇒ r = \(\frac{1}3\) mm
∴ Diameter of cross section = (1/3) × 2 mm
= 0.67 mm
NOTE:
When one figure is converted into another figure,the volume of two figures remain same.
