AP® Physics 1 & 2

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Loop of Wire in Magnetic Field


A $9.0\text{ V}$ battery is placed in a holder that will allow it to rotate freely. A wire of length $68\text{ cm}$ is formed into a loop, attached to the two ends of the battery and then placed in a magnetic field between a north pole of one bar magnet and the south pole of a second magnet as shown below.

The two sections of the wire (labeled $A$ and $B$) that are in the magnetic field each have a length, $L$, of $22\text{ cm}$. These segments are parallel to each other as well as the ends of bar magnets and are perpendicular to the magnetic field between the two magnets.

Laura L. Lang. Created for Albert.io. Copyright 2016. All rights reserved.

Note: the picture is not drawn to scale.

Which of the following values most closely approximates the magnitude of the magnetic force, $F_{\small{M}}$, on the section of the loop of wire labeled $A$ if the magnetic field strength, $B$, is $1.6\text{ T}$ and the resistance in the loop of wire, $R$, is $4.5\ \Omega$?


$2.2\text{ N}$


$1.4\text{ N}$


$0.70\text{ N}$


$0.18\text{ N}$