Finding the torque on a wire between two poles

  • Thread starter LuigiAM
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Homework Statement


[/B]
A rectangular wire of length 3 cm and width 2 cm is suspended vertically between two poles producing a uniform field of 2 T. Calculate the maximum torque acting on the wire.


Homework Equations



Torque = AIB sin(Θ)
Maximum torque is when sin(Θ) = 1, so Maximum Torque = AIB

The Attempt at a Solution



Tmax = AIB

Tmax = I(0.03)(0.02)(2)

Tmax = 0.0012 I

Using the formula from the notes I feel like I can find the maximum torque in terms of the current I. Is there a way to obtain the torque without the current? I believe there is information missing in the question. All similar questions found on google or in the book always either give the current or give enough information to derive it. I haven't found a single such question without the current...
 

Answers and Replies

  • #2
kuruman
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Without a current, there is no magnetic moment of the loop and therefore no torque. You need a number for the current to find a number for the torque.
 
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Thanks for the reply.

I think I'm just going to try the safe side and give the answer in terms of I but add a that if there is no current then there is no torque?
 
  • #4
kuruman
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I think I'm just going to try the safe side and give the answer in terms of I but add a that if there is no current then there is no torque?
Is this part of an online homework set of problems graded by some algorithm? If so, a numerical answer might be expected while the omission is in the statement of the problem. You may wish to ask your instructor. Otherwise, leaving the answer as τmax = 0.0012 I (I in Amp, τ in N⋅m) should be good enough. The units in parentheses are needed because you have a mix of numbers and symbols. That there is no torque when there is no current is implicit in the expression when someone sets I = 0.
 
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  • #5
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No, it's a paper homework and we're expected to submit answers on paper. I like that better honestly.

Thanks for reminding me about including the units! I often forget to include them in my answers
 
  • #6
kuruman
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No, it's a paper homework and we're expected to submit answers on paper. I like that better honestly.

Thanks for reminding me about including the units! I often forget to include them in my answers
You're good to go.
 
  • #7
haruspex
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give the answer in terms of I
Thanks for reminding me about including the units!
Need to be a bit careful quoting units on an answer which is a mix of numerics and unknowns. E.g. if you have a mass M (no units specified) and an acceleration of 2m/s2 then the force is 2M m/s2, not 2M Newtons.
 
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