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A long straight wire of length 2 m and mass 250 g is suspended horizontally in a uniform horizontal magnetic field of 0.7 T. The amount of current flowing through the wire will be ($g=9.8\ ms^{-2}$):
A
2.45 A
B
2.25 A
C
2.75 A
D
1.75 A
Detailed Solution
For the wire to be suspended (in equilibrium), the magnetic force balances gravity: $mg=i\ell B\Rightarrow250\times10^{-3}\times9.8=i\times2\times0.7\Rightarrow i=\dfrac{0.250\times9.8}{2\times0.7}=1.75$ A.