# A coil of 25 turns of wire is suspended by a thread

• Astraithious
In summary, the conversation discusses the reduction of tension in a thread when a current flows through a coil of wire. The correct solution involves taking into account the number of wraps of wire and using the formula F=IBL. The final answer is 0.16 amps.
Astraithious

## 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

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

then I tried combining the two

to get
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

Astraithious said:
1
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

Did you take into account that there are 25 wraps of wire?

Haha I did however I did 0.04 = I 0.065x25x0.15, not 0.04 = I 0.065x(25x0.15)

Thank you so much lol, i knew it was simple but it was killing my soul with frustration

## 1. What is the purpose of suspending a coil of wire with a thread?

The purpose of suspending the coil of wire with a thread is to create a simple pendulum, which can be used to demonstrate the principles of electromagnetism and energy conversion.

## 2. How does the number of turns in the coil affect its behavior?

The number of turns in the coil affects its behavior by increasing its sensitivity to changes in magnetic fields. This means that the more turns there are, the stronger the electromagnetic force produced by the coil will be.

## 3. What materials are typically used to make the coil?

The coil can be made from a variety of materials, but the most commonly used are copper wire and magnet wire. These materials have high conductivity and are able to efficiently transmit electric currents.

## 4. How is the coil connected to a power source?

The coil is connected to a power source by attaching one end of the wire to the positive terminal and the other end to the negative terminal. This allows for current to flow through the coil and create an electromagnetic field.

## 5. Can the coil of wire be used for anything other than demonstrations?

Yes, the coil of wire can be used in many practical applications, such as electric motors, generators, and transformers. Its ability to convert electrical energy into mechanical energy and vice versa makes it a valuable component in many electronic devices.

Replies
19
Views
2K
Replies
49
Views
4K
Replies
4
Views
2K
Replies
1
Views
1K
Replies
2
Views
2K
Replies
4
Views
4K
Replies
13
Views
8K
Replies
7
Views
5K
Replies
9
Views
6K
Replies
1
Views
2K