FYKOS Year 35 Series 3 Problem 3 — two solenoids · FYKOS 35 #35.3.3

Physics · electromagnetism

Problem

Consider two coils wound around a common paper roll. First coil has a winding density of

10\,\mathrm{cm^{-1}}

and the second coil has a winding density of

20\,\mathrm{cm^{-1}}

. The paper roll is

40\,\mathrm{cm}

long and has

1\,\mathrm{cm}

in diameter. Both coils are wound along the whole length of the roll, with the second coil wound around the first one. Considering the dimensions of the roll, we can neglect the boundary effects and assume that the coils behave as perfect solenoids. Now consider connecting the coils in series. This configuration can be substituted by a circuit with a single coil. What is the inductance of the substituting coil?

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