Attraction between coaxial solenoids

[LordBerkley]

Can anyone help me understand why two coaxial solenoids separated by a distance x, with current flowing in the same direction in each solenoid, would be attracted to each other using the right hand rule?

Im sure they would be attracted to one another (with the current flowing in the same direction, the poles are arranged N-S / N-S), but when i try to use the right hand rule I end up saying that there would be a repulsive force.

Anybody know where I'm going wrong?


Any help appreciated


LB

 

[jartsa]

Let's consider a small solenoid in the magnetic field of a large solenoid. Using the right hand rule we see that the small solenoid is not attracted or repelled, it's streched. (radially)


Let's say the small solenoid is elastic. When it enlarges, the direction of the magnetic field that it's in gradually changes.


So: First we imagine a small solenoid, we are using the right hand rule, our thumb is pointing in the direction of the streching force pulling some part of the solenoid, then we start turning our middle finger away from the axis of the solenoid, our thumb is turning to the appropriate direction.

 

[LordBerkley]

Thank you for the reply, but is there a way you can show that graphically?

I've attached a diagram of why I think using the right hand rule the solenoids would repel if that helps.

 

[jartsa]

There is a repelling force then, let's believe whatewer the right had rule says. But there's an attractive force at the other ends of the coils.

The repelling forces in the picture are actually attractive forces towards the other end of the same coil.(I would advice leaving one coils magnetic field out of the picture)

 

[pmacias]

The attraction between two coaxial solenoids can be explained by the magnetic fields produced by the current flowing through the solenoids. When current flows through a solenoid, it generates a magnetic field around it. This magnetic field is in the form of concentric circles around the solenoid.

When two coaxial solenoids are placed close to each other, the magnetic fields from each solenoid interact with each other. This interaction results in an attractive force between the two solenoids. The direction of this force can be determined using the right hand rule.

If you use your right hand to wrap your fingers around one solenoid in the direction of the current flow, your thumb will point in the direction of the magnetic field created by that solenoid. Similarly, if you wrap your fingers around the other solenoid in the same direction of current flow, your thumb will again point in the direction of the magnetic field created by that solenoid.

Now, using the right hand rule, if you point your thumb in the direction of the magnetic field of one solenoid and your fingers in the direction of the magnetic field of the other solenoid, your palm will face towards the other solenoid. This indicates that there is an attractive force between the two solenoids.

It is important to note that the direction of the magnetic field depends on the direction of the current flow. If the current flows in opposite directions in the two solenoids, the magnetic fields will also be in opposite directions, resulting in a repulsive force between the solenoids.

In summary, the attractive force between two coaxial solenoids is a result of the interaction between their magnetic fields, which can be determined using the right hand rule. If you are still getting a repulsive force, make sure you are using the correct direction of the magnetic fields based on the direction of the current flow in each solenoid.