# Finding the torque on a wire between two poles

## Homework Statement

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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...

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kuruman
Homework Helper
Gold Member
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.

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?

kuruman
Homework Helper
Gold Member
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.

LuigiAM
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

kuruman
Homework Helper
Gold Member
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.

haruspex