# Why in a solenoid, do the magnetic field lines resemble that of a bar magnet?

Each loop in the solenoid will have its own magnetic field wrapped around it. In that case it won't resemble the magnetic lines formed by a bar magnet...; but we see that it is the same. Why is that?

By applying Fleming's Right Hand in each turn, we get magnetic field lines that look like this :-

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But Magnetic field lines never intersect. They interact with the fieds of the surrounding turns of solenoid to form a combined magnetic field which looks like this:-

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From www.nde-ed.org :-

The magnetic field circling each loop of wire combines with the fields from the other loops to produce a concentrated field down the centre of the coil. A loosely wound coil is illustrated to show the interaction of the magnetic field. The magnetic field is essentially uniform down the length of the coil when it is wound tighter.

If the loops or turns are extremely close to each other, magnetic field lines between neighbouring turns effectively cancel, resulting in straight magnetic fields inside the solenoid, similar magnetic fields inside a bar magnet :-

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The magnetic field lines around (a) a bar magnet and (b) a current carrying solenoid :-

EDIT

As in the case of bar-magnets, the magnetic field is stronger inside the solenoid than outside it. Magnetic field lines are closely packed inside the solenoid, and magnetic field is concentrated into a nearly uniform magnetic field inside the solenoid. The magnetic fields outside are weak and spread out.

The first three diagrams are snipped from a video available on YouTube: Concepts in physics - Electromagnetism

• Maybe you could improve this by making clear why the field is much stronger inside the solenoid than on the outside. (The second and third figures in isolation don't make this point clear). Also if this is directly quoted from another source could you provide the appropriate credit/attribution. Oct 26, 2014 at 8:11
• For inside and outside I think it is easy reason. Inside is near the field line in every direction while outside is far away from other Oct 26, 2014 at 10:32
• i dont understand...we only consider to pairs of concentric circles in this case. But we should not forge that there are a LOT of pairs of concentric circles all around the loop at every point Oct 4, 2016 at 12:54

Opposite. Solenoid is actually like real magnet bar

Imagine one iron atom. It has electrons run in circle around that atom so it generate magnetic force. Every iron atom is like a solenoid loop by itself

Then Imagine a bar magnet is clump of iron which almost all atoms align in the same direction so every atom contribute a magnetic force. That's it much more like many solenoid loops parallel to each other

In detail you should watch this video