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could really use some help with these two magnetism questions. A metal bar of ma

ID: 1411567 • Letter: C

Question

could really use some help with these two magnetism questions.

A metal bar of mass M slides without friction on top of two conducting rails. The rails are connected to a battery and resistor as shown. The entire system sits inside a magnetic field rightarrow B that points into the page. Find the acceleration of the bar in terms of M, B, epsilon, R, and L. What direction does the bar accelerate? A semicircular wire of radius r is connected to a battery with EMF epsilon and a resistor R as shown. The whole circuit is placed inside a magnetic field rightarrow B that points into the page. Find the magnetic force (magnitude and direction) on the bottom straight wire in terms of epsilon, R, r and B. Imagine a tiny segment of the semicircular wire with length dl located at an angle theta from the x axis. Find the magnitude of the tiny magnetic force dF acting on this segment in terms of epsilon, R, r and the tiny angle d theta subtended by the segment. Find the components dF_x and dF_y of the force on the tiny segment. Integrate to get the x and y components of the total force rightarrow F on the semicircular wire.

Explanation / Answer

3

i = current flowing in the bar

using ohm's law

i = E/R

magnetic force on the bar is given as

F = i BL = EBL/R

we know that

F = Ma

so a = F/M = EBL/(RM)