The Figure below shows a possible device for measuring magnetic fields. A loop c

Question

The Figure below shows a possible device for measuring magnetic fields. A loop carrying a current I is dipped into a region of magnetic field. The loop is suspended from a spring of constant that stretches if the magnetic field points in the direction indicated. Here the loop has width l = 1.50 cm, I = 1.20 mA, the spring stretches 4.00 mm, = 4.00×10-4 N/m and the magnetic field is uniform. What is the magnitude of the field? Is the current direction clockwise? Recall that the spring force is given by Hooke’s Law.

Explanation / Answer

Magnetic force = spring force

=> i*L*B = k*x

=> B= 4*10^-4*4*10^-3/(1.5*10^-2*1.2*10^-3) =0.0888 T

From right hand rule, current will be anti-clock wise direction.

( Since spring is stretched, it means magnetic force is in downward direction. Now keep your hand bottom width of rectangle such that thum points towards right and remaining four fingers towards upside or spring side. Now curl the four fingers/palm towards direction of magnetic force i.e here downwards. Direction of thumb is direction of flow of current. Here we assumed right and it came correct. )

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