Answer
Given,
Length of the wire,L = 31 cm = 0.31 m
mass of the wire, m = 9 g = 0.009 Kg
Current in the wire,I = 7 A
Magnetic field strength, B= ?
Equating magnetic force to the weight of the wire.
[tex] BIL = m g[/tex]
[tex] B=\dfrac{m g}{IL}[/tex]
[tex] B=\dfrac{0.009\times 9.81}{7\times 0.31}[/tex]
B = 0.0407 T
For Force to be upward magnetic field direction should be outward of the plane of paper.
