Magnetic Effects Of Current Question 137
Question: Two coaxial solenoids 1 and 2 of the same length are set so that one is inside the other. The number of turns per unit length are $ n_{1} $ and $ n_{2} $ . The currents $ i_{1} $ and $ i_{2} $ are flowing in opposite directions. The magnetic field inside the inner coil is zero. This is possible when [Roorkee 2000]
Options:
A) $ i_{1}\ne i_{2} $ and $ n_{1}=n_{2} $
B) $ i_{1}=i_{2} $ and $ n_{1}\ne n_{2} $
C) $ i_{1}=i_{2} $ and $ n_{1}=n_{2} $
D) $ i_{1}n_{1}=i_{2}n_{2} $
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Answer:
Correct Answer: C
Solution:
$ B_{net}=B_{1}-B_{2}\Rightarrow B_{1}-B_{2}=0\Rightarrow B_{1}=B_{2} $
$ \Rightarrow B\propto ni. $ So $ n_{1}i_{1}=n_{2}i_{2} $ or $ n_{1}=n_{2},\text{and }i_{1}=i_{2} $
BETA
