I have a copper cable - with outer diameter of $3.5\; mm$. Length is $182\; cm$ or $6\; feet$. Now I have a thread with the diameter of $0.12\; mm$. I need to cover the entire surface area of this cable with this thread by braiding or winding it over & over again. How much length of the thread would I need?
I tried using $2\pi r h$ divide by half of surface area of the thread but it threw up an insane number.
Please help?
Think of the thread as a thin plate $0.12 \text{ mm}$ large and at distance $1.75 + 0.06 \text{ mm}$ of the axis. It forms a cylindre of area
$$2\pi\cdot1.81\cdot1820\text{ mm}^2,$$ corresponding to
$$\frac{2\pi\cdot1.81\cdot1820}{0.12}\text{ mm}\approx 17.248\text{ m}.$$