CBSE Class 10 Answered
Let's imagine the cylinder the hollow and we cut it open.
Now it's like a rectangle, with width = circumference, and length = length of the cylinder.
One wrap or turn of the copper wire covers an are of widthxdiameter of copper wire = 2πRxd =
2x3.14x 50 mmx 3 mm = 942 mm2.
So a length of 2πR = 2x3.14x 50 mm = 314 mm of copper wire covers an area of 942 mm2
Curved surface of cylinder = 2 x 3.14 x 50 mm x 120 mm = 37680 mm2
length of copper wire, = 37680x 314/942 = 12560 mm = 1256 cm
Volume of wire = πd2L/4 = 3.14x0.09x1256/4 = 88.74 cm3
Mass of wire = density x volume = 8.88x88.74 = 788.01 gm = 0.788 kg.
Hence,
Length of copper wire = 1256 cm.
Mass of copper wire = 0.788 kg.
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