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The flux density at a point in space is given by B = 4x aₓ − 2ky a_y − 8z a_z Wb/m². The value of constant k must be equal to

1. -2
2. -0.5
3. +0.5
4. +2

Correct answer: -2

Solution

Since B is a magnetic flux density, div B = 0. Computing: d/dx(4x) + d/dy(-2ky) + d/dz(-8z) = 4 - 2k - 8 = 0, which gives k = -2.

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