# Current and Magnetic Poles of a Solenoid (Diagram) & Right Hand Thumb Rule

Well, my doubt's pretty elementary.

Firstly I wanted to confirm whether both the cases, as illustrated in the picture, are correct. I've darkened the part of each coil that faces us. Using the clock-rule both are right. Even on the net I've seen these two variations.

In the practical sense, can we say that one of these diagrams is more accurate than the other? I've not much idea about the working of a solenoid in a lab. Like about the connections and stuff. I'd probably guess that both are one and the same but would like to confirm it.

Secondly, I have quite an elementary school-level understanding of these topics and wanted to confirm another thing. In such cases if we curl the fingers of our right hand in the direction of current in one loop of the solenoid the thumb should point to the left hand side (Right Hand Thumb Rule). So it means that the field is towards the left inside the solenoid. We can identify the poles on this basis, right?

• Both cases are identical. The current in the wires nearest to you is upwards in both cases and the current in the part of the wires furthest from you is downwards in both cases. In both cases if you look at the solenoid from the South pole the current is going clockwise in both cases.
– KDP
Commented Feb 11 at 17:39
• A solid +1 for drawing the picture! I wish all questions on Physics.SO, whether simple or complex, were this thoroughly prepared! Commented Feb 12 at 4:46
• Just noting that your diagram shows which pole is which if you replace the solenoid by a bar magnet, ie the poles seen from outside the solenoid. You have correctly applied the RH thumb (or grip) rule - the field comes out of the North pole of the magnet. Commented Feb 12 at 11:47

Huh, a nice illustration!

I wanted to confirm whether both the cases, as illustrated in the picture, are correct.

Note that both solenoids form the right screw. No translation or rotation in 3D-space may possibly turn a right screw into a left screw, or other way around. If they were a bolt with the head on the left, following the arrows would move the bold to the left from a fixed nut. That's all you need to know to confirm that both pictures show the same solenoid.

Ignore the leads to avoid confusion: if there is current in the wire, then there is some way it's supplied to the solenoid, it's just outside of the frame of the picture. Roughly,

You're looking at the same screw, not dead-on to the side, but slightly from the right on the top picture, from left on bottom.

can we say that one of these diagrams is more accurate than the other?