Magnetic Effects Of Current Question 47
Question: Two concentric circular coils of ten turns each are situated in the same plane. Their radii are 20 and 40 cm and they carry respectively 0.2 and 0.3 ampere current in opposite direction. The magnetic field in $ weber/m^{2} $ at the centre is [MP PMT 1994]
Options:
A) $ \frac{35}{4}{\mu_{0}} $
B) $ \frac{{\mu_{0}}}{80} $
C) $ \frac{7}{80}{\mu_{0}} $
D) $ \frac{5}{4}{\mu_{0}} $
Show Answer
Answer:
Correct Answer: D
Solution:
Two coils carrying current in opposite direction, hence net magnetic field at centre will be difference of the two fields. i.e. $ B_{net}=\frac{{\mu_{0}}}{4\pi }\cdot 2\pi N[ \frac{Ni_{1}}{r_{1}}-\frac{i_{2}}{r_{2}} ] $ $ =\frac{10{\mu_{0}}}{2}[ \frac{0.2}{0.2}-\frac{0.3}{0.4} ]=\frac{5}{4}{\mu_{0}} $
BETA
