A uniform bar of length L carries a current I in the direction from point a to point b (Fig. P27.70). The bar is in a uniform magnetic field that is directed into the page. Consider the torque about an axis perpendicular to the bar at point a that is due to the force that the magnetic field exerts on the bar.

(a) Suppose that an infinitesimal section of the bar has length dx and is located a distance x from point a. Calculate the torque dt about point a due to the magnetic force on this infinitesimal section.

(b) Use Ï„ = ˆ«^b_a dÏ„ to calculate the total torque t on the bar.

(c) Show that t is the same as though all of the magnetic force acted at the midpoint of the bar.

Figure P27.70

Transcribed Image Text:

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