This question was asked in 2012 cbse board exam. Question from RS Aggarwal book chapter volume and surface area of solid, page number 810, exercise 17B, problem number 7.

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# A copper rod of diameter 2 cm and length 10 cm is drawn into a wire of uniform thickness and length 10 m. Find the thickness of the wire

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Given data,

The radius of the copper rod, R = 2/2 = 1cm

The height of the copper rod, H = 10 cm

The height of the wire, h = 10 m = 1000 cm

Volume of the wire = Volume of the rod

Ï€rÂ²h = Ï€RÂ²H

rÂ²h = RÂ²H

rÂ² * 1000Â = 1 * 10

rÂ² = 1/100

r = âˆš[ 1/100]

r = 1/10

r = 0.1 cm

Diameter of the wire = 2r

= 2 * [0.1]

= 0.2 cm

âˆ´ Thickness of the wire = 0.2 cm

âˆ´ Thickness of the wire = 2 mm