Calculate the current in the coil

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Homework Help Overview

The discussion revolves around calculating the current in a circular coil subjected to a magnetic field, involving parameters such as the number of turns, area, magnetic field strength, and torque. The original poster presents a problem involving a coil with 394 turns and an area of 0.78 m² in a magnetic field of 0.8 T, where the maximum torque is given as 0.0059 N·m.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to apply the torque formula to find the current but questions the role of the number of turns in their calculations. Some participants suggest alternative formulations and clarify the relationship between torque, current, and the number of turns. There is also a discussion about a second part of the question involving a larger coil and the need to determine the area based on the length of the wire.

Discussion Status

Participants are actively engaging with the problem, exploring different interpretations of the equations involved. Some guidance has been offered regarding how to approach the geometry of the coil and the calculations needed to find the current in both the original and larger coil scenarios. The conversation reflects a collaborative effort to clarify misunderstandings and refine the approach to the problem.

Contextual Notes

There is a noted complexity in transitioning from a multi-turn coil to a single-turn coil with a larger area, leading to questions about the implications of these changes on the calculations. The original poster expresses confusion about the relationship between the number of turns and the torque, indicating a need for further clarification on these concepts.

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Homework Statement



A circular coil of 394 turns and area 0.78 m2
is in a uniform magnetic field of 0.8 T. The
maximum torque exerted on the coil by the
field is 0.0059 N · m.
Calculate the current in the coil. Answer in
units of A

Homework Equations


torque= i*A*B



The Attempt at a Solution



what i did is that i solved for the current using the above equation i= torque/(A*B) but i keep getting the wrong answer .. i think because of the number of turns but i don't know were to include it

i need ur help thanks in advance
 
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Torque = μ X B, where μ = nIA.
 
so is it
i = torque /(number of turns *A*B)
 
mba444 said:
so is it
i = torque /(number of turns *A*B)
Yes.
 
Assume the 394 turns of wire are used to form
a single-turn coil with the same shape but
much larger area.
What is the current if the maximum torque
exerted on the coil by the field is 0.0059 N · m?


this a second part of the question but i really didnt understand the difference
 
You need to figure out the area of this larger coil. Hint: What's the length of the wire?
 
i tried to figure out the length where i came up with this equation but still i couldn't figure what to put for the F

length = F/(i*B)

im kind of lost
 
Figuring out the length of the wire is a geometry problem. You had a coil of a given area and number of turns. What was the circumference of that coil?
 
C= 2*pi*r
 
  • #10
mba444 said:
C= 2*pi*r
Good. Use the known area to find the radius.
 
  • #11
ok i did so know
1 loop = 2*pi*r (i just found)
394= X
so do i do the cross multiplication to solve for X which is the new area
 
  • #12
mba444 said:
ok i did so know
1 loop = 2*pi*r (i just found)
394= X
so do i do the cross multiplication to solve for X which is the new area
Do this:
Use the area of the original coil to solve for the radius, using A = pi*r².
Use the radius to find the length of each loop, using the circumference formula.
Find the total length of the wire by multiplying the length of each loop by the number of loops.
That becomes your new circumference of your big coil. Work backwards to find, its radius then area.
 
  • #13
ok thanks a lot i got it know .. sorry if i wasted your time
 
  • #14
i got for the larger area = 121084 m^2

i plugged in this eqs i = (.0059)/(394*121084*0.8)

but i got the wrong answer =(
 
  • #15
mba444 said:
i got for the larger area = 121084 m^2
That looks OK.

i plugged in this eqs i = (.0059)/(394*121084*0.8)
When used to make the giant coil there's only one turn.
 
  • #16
thanx again i got the right answer
 

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