Question

The force acting per unit length of a semi circular wire of radius R carrying a current I is:​

Answer 1

Force on a conductor in a magnetic field is given by, F = ILBsinθ

θ is the angle between the direction of current and magnetic field

Since, you  haven't mentioned any information on the orientation of the coil in the magnetic field I shall assume θ to be 90º

so, F = ILB

Force per unit length, F/L = ILB/L = IB

So the force acting per unit length of a semi circular wire of radius R carrying a current I is IB

Hope it helps!

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