Multiple choice

The curved surface of a cylinder is 1000 cm2 .A wire of diameters 5 mm. is wound around it ,so as to cover it completely .What is the length of the wire used?

  1. 22 m.

  2. 20 m.

  3. 18 m.

  4. 34 m.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

CSA of cylinder = 2πrh = 1000 cm². Wire diameter = 5 mm = 0.5 cm, so radius = 0.25 cm. When wire is wound, each turn uses 0.5 cm (diameter) of cylinder height. Number of turns = h/0.5. Length per turn = 2πr. Total length = 2πr × (h/0.5) = 2πrh/0.5 = 2×1000/0.5 = 4000 cm = 40 m. Wait - checking options again. Option B says 20 m. Let me reconsider: if CSA = πdh and wire length L × πd = πd × (h/0.5) = πdh/0.5 = CSA/0.5 = 1000/0.5 = 2000 cm = 20 m. Option B is correct.

Keep practicing — related questions