Which way does this coil turn in a magnetic field?

In summary, the direction in which a coil turns in a magnetic field is determined by the right-hand rule and the orientation of the current flowing through the coil. When a current passes through the coil, the interaction between the magnetic field and the magnetic field created by the current generates a torque that causes the coil to rotate. The specific direction of rotation (clockwise or counterclockwise) depends on the direction of the current and the orientation of the magnetic field.
  • #1
maxelcat
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Homework Statement
A plan of a moving coil meter is given and a side view which shows direction of B field and current. We are asked to find the direction of rotation.
Relevant Equations
Flemings left hand rule
I use FLHR and the plan diagram. This suggests that the left hand side of the coil is going down. I have added annotations to this, which agree with the mark scheme which then goes onto suggest that the coil turns clockwise. To me though this would make it go anti clockwise.

So... what am I missing please
 

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  • #2
maxelcat said:
I use FLHR and the plan diagram. This suggests that the left hand side of the coil is going down. I have added annotations to this, which agree with the mark scheme
Agree. Left edge of coil moves 'into page' (down); right edge moves 'out of page' (up).

maxelcat said:
then goes onto suggest that the coil turns clockwise. To me though this would make it go anti clockwise.
So... what am I missing please
The direction (CW or ACW) depends on which end of the coil (top or bottom) the pointer is attached to (so which end you are looking at). The diagram doesn't show this. I would (like you) assume the pointer is attached to the bottom, but I guess that's not the intention.

But you have understood the physics correctly, which is what really counts!

Minor edits.
 
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  • #3
thanks for your reply. Having now looked at the examiners report, and bearing in mind this was 2021 when things seemed to be up in the air exam wise, I think they wanted you to justify - so if you said something along the lines of 'looking at the plan view into the page' or 'assuming the pointer is on the bottom end of the side view'.... then you could answer acw etc
 

FAQ: Which way does this coil turn in a magnetic field?

How can I determine the direction a coil will turn in a magnetic field?

The direction a coil will turn in a magnetic field can be determined using Fleming's Left-Hand Rule. Point your thumb, first finger, and second finger of your left hand perpendicular to each other. The first finger represents the direction of the magnetic field (from North to South), the second finger represents the direction of the current, and the thumb will point in the direction of the force (motion) on the coil.

What factors influence the direction of rotation of a coil in a magnetic field?

The direction of rotation of a coil in a magnetic field is influenced by the direction of the current flowing through the coil and the orientation of the magnetic field. Reversing either the current or the magnetic field will reverse the direction of rotation.

What happens if the current direction in the coil is reversed?

If the current direction in the coil is reversed, the direction of the force on each side of the coil will also reverse, causing the coil to turn in the opposite direction.

How does the shape and orientation of the coil affect its rotation in a magnetic field?

The shape and orientation of the coil can affect the torque and efficiency of its rotation. A coil that is aligned perpendicular to the magnetic field lines will experience maximum torque. The number of turns in the coil and the shape (e.g., circular, rectangular) can also influence the performance and stability of the rotation.

Can a coil rotate continuously in a magnetic field, and how is this achieved?

Yes, a coil can rotate continuously in a magnetic field if it is part of a motor. This is typically achieved by using a commutator or electronic switching to periodically reverse the direction of current in the coil, ensuring continuous rotation. This setup allows the coil to keep turning in one direction by continuously changing the direction of the force acting on it.

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