Magnetic field far from a solenoid

In summary, the magnetic field inside a solenoid is μIn/L and outside is 0 (when the point is near the solenoid). However, if the solenoid is long and the point is far from it (and perpendicular to it), the magnetic field would behave like a wire and be μI/2πR. This is because the solenoid can be thought of as a sum of infinitely small perpendicular turns, making it equivalent to a long straight wire. Even if the solenoid is not infinitely long, the field outside would still be the same as a single wire if it is wound in a spiral.
  • #1
jaumzaum
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I know the magnetic field inside the solenoid is μIn/L and outside is 0 (provided that the point is near the solenoid).

But if we had a long solenoid and choose a point far from the solenoid (and perpendicular to it), would it behave like a wire? Would the magnetic field be μI/2πR?
 
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  • #2
jaumzaum said:
I know the magnetic field inside the solenoid is μIn/L and outside is 0 (provided that the point is near the solenoid).

But if we had a long solenoid and choose a point far from the solenoid (and perpendicular to it), would it behave like a wire? Would the magnetic field be μI/2πR?

If the solenoid is wound as a spiral, which it usually is, then the field outside it would be the same as a long straight wire. That's because the coil inside has to be wound continuously from end to end. You can think of the coil as the sum of N (N→ ∞) perfectly perpendicular turns, each with a small gap, and a long single wire joining all the turns at the gaps. Whether the gaps are all lined up or random or any other orientation makes no diff.

In fact, even if the solenoid is not of infinite length, the field outside would be the same as if it was just a single wire, again if it was wound in a spiral.

http://en.wikipedia.org/wiki/Solenoid
 
  • #3
Thanks man
 

FAQ: Magnetic field far from a solenoid

What is a solenoid?

A solenoid is a coil of wire that is tightly wound in a helical shape. When an electric current flows through the coil, it creates a magnetic field.

How does the magnetic field far from a solenoid differ from the magnetic field near the solenoid?

The magnetic field far from a solenoid is weaker and more spread out compared to the magnetic field near the solenoid. This is because the strength of a magnetic field decreases with distance from its source.

What factors affect the strength of the magnetic field far from a solenoid?

The strength of the magnetic field far from a solenoid is affected by the number of turns in the coil, the amount of current flowing through the coil, and the distance from the solenoid.

Can the direction of the magnetic field far from a solenoid be changed?

Yes, the direction of the magnetic field far from a solenoid can be changed by reversing the direction of the electric current flowing through the coil. This is known as the right-hand rule, where the direction of the magnetic field is determined by the direction of the current using your right hand.

How is the magnetic field far from a solenoid used in everyday life?

The magnetic field far from a solenoid is used in various applications, such as in electric motors, generators, and magnetic resonance imaging (MRI) machines. It is also used in security systems, credit cards, and speakers.

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