A confusion with tangent galvanometer

AI Thread Summary
The discussion centers on the behavior of a coil in relation to Earth's magnetic field when no current is passed through it. Initially, the coil shows no deflection, indicating that its magnetic field aligns with Earth's horizontal field. However, confusion arises regarding the expected perpendicular relationship between the coil's magnetic field and Earth's field when current flows through the coil. It is clarified that the coil's magnetic field is ideally perpendicular to its plane, and when oriented correctly, the coil's field will be at right angles to Earth's field. The conversation concludes with an understanding of how the compass behaves in this setup, highlighting the importance of orientation in magnetic field interactions.
Rishavutkarsh
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When no current is passed through the coil it shows no deflection i.e. B is in the direction shown. But according to theory both fields should be perpendicular (Earth's horizontal field and the one due to coil).
But I am confused because the coil would ideally create a magnetic field that is either parallel or anti-parallel to Earth's Horizontal magnetic field. Is there somewhere I made a blunder or am I missing something?
 

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Rishavutkarsh said:
But I am confused because the coil would ideally create a magnetic field that is either parallel or anti-parallel to Earth's Horizontal magnetic field.
If that happens, rotate the device by 90 degrees, then they are perpendicular to each other. The orientation of the magnet without current helps to find the right orientation.
 
What do you mean by "ideally" in this case? I simply don't know why you say that the parallel fields or antiparallel fields configurations are "ideal".
 
mfb said:
If that happens, rotate the device by 90 degrees, then they are perpendicular to each other. The orientation of the magnet without current helps to find the right orientation.
Yeah that's what I thought too but as far as I know this is the way this device is used (Without rotating it).

Philip Wood said:
What do you mean by "ideally" in this case? I simply don't know why you say that the parallel fields or antiparallel fields configurations are "ideal".
I mean the field lines created by a coil are exactly perpendicular to it's plane 'ideally'.
 
Rishavutkarsh said:
I mean the field lines created by a coil are exactly perpendicular to it's plane 'ideally'.
That's correct, but it's not what you said before!
You orientate the coil with its plane in the Earth's magnetic North-South meridian plane. So the coil's field (at its centre) is in the East-West direction, that is at right angles to the Earth's field. With no current through the coil a compass (or magnetometer) magnet placed at the centre of the coil will point magnetic North. As soon as you have a current through the coil it will deflect from North.
 
I got it that's correct; Thank you. I got confused a bit by that compass and magnet.
 
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