- #1

Astraithious

- 20

- 0

## Homework Statement

A coil of 25 turns of wire is suspended by a thread. When a current flows through the coil, the tension in the thread is reduced by 4.0 ´10-2N.

http://members.shaw.ca/barry-barclay/Self-Tests/test11/Magnet20.gif

## Homework Equations

F=IBL

B=nμI[/B]

## The Attempt at a Solution

I have been driving myself nuts with this question haha but here is my attempt.

The force against gravity has to come from the current so I tried

**0.04 = I (0.065)(0.15)**

I = 4.1a, which is incorrect

I = 4.1a

then I tried combining the two

**to get**

I=√F/Nμ

I=√F/Nμ

but that left me with

**35.68**

So I am at a loss as to how to go about this , any help would be great! or any formulas I am missing. I have not done calc yet this is all supposed to be simple algebra however this process for this particular question eludes me and it is the last of the set of 190 , I want it done! haha

Correct answer is

**.16 amps**I know it has to go counterclockwise for the force to be pushing up