InterviewSolution
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InterviewSolution
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A thin insulated wire form a spiral of N= 100 turns carryinga current of i=8 mA . The inner and outer radii are equal to a = 5cm and b=10 cm . Find the magnetic field at the centre of the coil. |
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Answer» SOLUTION :Let n = no. of turns PER unit length along the radial of spiral. Consider a ring radii X and x + dx. No. of turns in the ring = ndx. `n = (N)/((b-a))` Magnetic FIELD at the centre due to the ring . `dB = (mu_0(ndx)i)/(2x)` So net field `B = int dB = int_(a)^(b)(mu_0nidx)/(2x) = (mu_0ni)/(2) int_a^b (dx)/(x)` `or B = (mu_0 ni )/(2) ln"" (b)/(a) or B = (mu_0Ni)/(2(b-a)) "ln"(b)/(a)` ` = (4pixx 10^(-7) xx 100 xx 8 xx 10^(-3))/(2(10 -5)xx10^(-2)) "ln"(10)/(5)` `B = 6.96 xx 10^(-6) T` |
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