# Magnetic Torques- is this an MCAT test topic?

#### minutemen11

##### Full Member
7+ Year Member
Hey guys i have no life (my MCAT is coming up real soon) and was looking at questions on Yahoo answers in the chem and physics categories because they tend to ask a some really good conceptual questions. Anyways this is someones question on Yahoo Answers, it IS NOT MINE (is that legal?). I was looking at it for a while and was wondering if something like this would show up on the mcat.

"So, i have no idea how to even start any of these. If you could explain how or give me an equation to get on the right track that would really help! There are 3 or 4 here. I just don't know where to begin any. Even if you can help with just one that would be great! Thank you so much

A conducting bar of length 0.20 m and mass 21.0 g is suspended by a pair of flexible leads in a uniform 0.10 T magnetic field (directed into the page) as shown in the figure. What is the current required to remove the tension in the supporting leads? Supply a "-" sign if the current must flow from right to left.

picture 1: http://i861.photobucket.com/albums/ab173/NorbertEh/HangingWire.jpg

A 62.0 cm wire carries a current of 2.40 A. The wire is formed into a circular coil and placed in a Magnetic Field of intensity 1.90 T. Find the maximum torque that can act on the loop.

The figure shows a rectangular loop of wire of 70 turns, 12.0 by 28.0 cm. It carries a curent of 1.06 A and is hinged at one side. What is the magnitude of the torque that acts on the loop, if it is mounted with its plane at an angle of 46.0 degrees to the direction of B, which is uniform and equal to 0.80 T?
picture: http://i861.photobucket.com/albums/ab173/NorbertEh/TorqueOnSquareLoop.gif

The diagram below depicts a wire carrying a current I = 4.80 A. The wire splits into two channels; of resistance = 7.45 and = 4.00 , and re-joins, forming a current loop in the shape of an isosceles triangle with base distance d = 5.75 cm and height L = 16.0 cm. The loop is entered into the space between the two poles of a magnet with a uniform magnetic field, B = 3.05 T, that runs from one pole to the other. The loop is placed such that the field lies in the plane of the loop. What is the magnitude of the torque on the circuit about the wire's axis?

picture: http://i861.photobucket.com/albums/ab173/NorbertEh/TriangularWire.gif."

once this is not my own question, its someone else's i found on yahoo answers...

#### Bernoull

##### Full Member
10+ Year Member
7+ Year Member
Hey guys i have no life (my MCAT is coming up real soon) and was looking at questions on Yahoo answers in the chem and physics categories because they tend to ask a some really good conceptual questions. Anyways this is someones question on Yahoo Answers, it IS NOT MINE (is that legal?). I was looking at it for a while and was wondering if something like this would show up on the mcat.

"So, i have no idea how to even start any of these. If you could explain how or give me an equation to get on the right track that would really help! There are 3 or 4 here. I just don't know where to begin any. Even if you can help with just one that would be great! Thank you so much

A conducting bar of length 0.20 m and mass 21.0 g is suspended by a pair of flexible leads in a uniform 0.10 T magnetic field (directed into the page) as shown in the figure. What is the current required to remove the tension in the supporting leads? Supply a "-" sign if the current must flow from right to left.

picture 1: http://i861.photobucket.com/albums/ab173/NorbertEh/HangingWire.jpg

This one seem to require u to equate gravitational force to magnetic force.
mgh = B x iL, u should get the current i by plug n chug. i should flow to da right..
(x= cross product)

A 62.0 cm wire carries a current of 2.40 A. The wire is formed into a circular coil and placed in a Magnetic Field of intensity 1.90 T. Find the maximum torque that can act on the loop.

t = u x B, u= iA (x= cross product), review magnetic moments if u dont know "u" (u like in micro)

The figure shows a rectangular loop of wire of 70 turns, 12.0 by 28.0 cm. It carries a curent of 1.06 A and is hinged at one side. What is the magnitude of the torque that acts on the loop, if it is mounted with its plane at an angle of 46.0 degrees to the direction of B, which is uniform and equal to 0.80 T?
picture: http://i861.photobucket.com/albums/ab173/NorbertEh/TorqueOnSquareLoop.gif

t = u x B, u= NiA (x= cross product), N= # of turns, if it's one like above it's ignored for u

The diagram below depicts a wire carrying a current I = 4.80 A. The wire splits into two channels; of resistance = 7.45 and = 4.00 , and re-joins, forming a current loop in the shape of an isosceles triangle with base distance d = 5.75 cm and height L = 16.0 cm. The loop is entered into the space between the two poles of a magnet with a uniform magnetic field, B = 3.05 T, that runs from one pole to the other. The loop is placed such that the field lies in the plane of the loop. What is the magnitude of the torque on the circuit about the wire's axis?

picture: http://i861.photobucket.com/albums/ab173/NorbertEh/TriangularWire.gif."

once this is not my own question, its someone else's i found on yahoo answers...

Too late in da nite for the last one, i might have to review some things.. Goodluck..

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