# What force does the current carrying coil feel?

• ybhathena
In summary, the right hand rule would be to point your fingers in the direction of the magnetic field, your thumb in the direction of the current, and your palm in the direction of the force.
ybhathena

## Homework Statement

What direction does the force that the current carrying coil feel point to when a magnetic field is turned on?

A magnetic field is turned on and points from bottom to top and passes through a current carrying coil that has current passing through it CCW. Here is a diagram https://stuff.mit.edu/afs/athena/course/8/8.02t/www/materials/PRS/Raw/PRS_W11D2.pdf
(bottom of page 2)

F = ILBsintheta

Lenz's law

## The Attempt at a Solution

From Lenz's law I know that once the magnetic field is turned on there is an increase in magnetic flux upwards. Which means there is an induced magnetic field downwards, which means there is a current passing through the wire that should be clockwise. But this question is weird because there is already current passing though the wire CCW, so I'm not sure exactly sure what happens to the current or the force when the magnetic field is turned on. I would really appreciate some help!

This question is about the force on the loop when there is a steady current in the loop. So, you don't need to worry about what happens when you first turn on the current or when you first turn on the magnetic field (when things are changing with time). So, Lenz's law is not relevant to this question.

Did you learn how to get the direction of the magnetic force on a steady current placed in a magnetic field using the "right hand rule"?

So the right hand rule would be fingers point in direction of B field, thumb in direction of conventional current and palm in direction of force, but in this case it's a weird more difficult to use since it's a loop rather than a straight wire.

You can look at small sections of the loop. A very short section is approximately straight. For example, consider a small section at the far right side of the loop where you see dF2 indicated. The picture below shows the cross-section of the wire at this point. Can you see how the right hand rule works there?

Note that the current in this section is essentially into the page

TSny said:
You can look at small sections of the loop. A very short section is approximately straight. For example, consider a small section at the far right side of the loop where you see dF2 indicated. The picture below shows the cross-section of the wire at this point. Can you see how the right hand rule works there?

View attachment 208303

Note that the current in this section is essentially into the page

Ohh I see it now. Your diagram really helped visualize it better. Thank you!

## 1. What is the force experienced by a current carrying coil?

The force experienced by a current carrying coil is known as the Lorentz force, which is the force exerted on a charged particle when it moves through an electric and magnetic field. This force is given by the formula F = q(E + v x B), where q is the charge of the particle, E is the electric field, v is the velocity of the particle, and B is the magnetic field.

## 2. How does the direction of the current affect the force experienced by the coil?

The direction of the current determines the direction of the force experienced by the coil. The force is perpendicular to both the direction of the current and the direction of the magnetic field. If the current is parallel to the magnetic field, there will be no force on the coil.

## 3. Does the strength of the current affect the force experienced by the coil?

Yes, the strength of the current does affect the force experienced by the coil. The higher the current, the stronger the force will be. This can be seen in the formula for the Lorentz force, as the force is directly proportional to the current.

## 4. What is the relationship between the magnetic field and the force experienced by the coil?

The magnetic field plays a crucial role in determining the force experienced by the coil. The force is directly proportional to the strength of the magnetic field. This means that as the magnetic field increases, the force experienced by the coil also increases.

## 5. How does the shape of the coil affect the force experienced by it?

The shape of the coil can affect the force experienced by it in two ways. Firstly, a larger coil will experience a stronger force compared to a smaller coil, assuming all other factors remain constant. Secondly, the orientation of the coil with respect to the magnetic field can also affect the force. A coil perpendicular to the magnetic field will experience a stronger force than a coil parallel to the magnetic field.

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