In a cylindrical coordinate system, a 2-m-long straight wire carrying a current of 5 A in...

In a cylindrical coordinate system, a 2-m-long straight wire carrying a current of 5 A in the positive z-direction is located at r = 4 cm, ϕ = π/2, and – 1 m ≤ z ≤ 1 m.

(a) If B = 0.2 cos ϕ (T), what is the magnetic force acting on the wire?

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(b) How much work is required to rotate the wire once about the z-axis in the negative ϕ-direction (while maintaining r = 4 cm)?

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(c) At what angle ϕ is the force a maximum?