Left hand rule
The explanation is that the force acts upwards due to newtons 3rd law. However I don’t quite understand why we consider the force like that. Why isn’t the force downwards since that’s the actual direction of the force as the scale increases
(edited 1 year ago)
Why doesn’t the same principle apply here? Since the actual direction of force is to the left, using the logic from above the force exerted will be reversed and acting towards the right by Newton’s third law?
Original post by The A.G
The explanation is that the force acts upwards due to newtons 3rd law. However I don’t quite understand why we consider the force like that. Why isn’t the force downwards since that’s the actual direction of the force as the scale increases
i didn't get this one for ages either, don't worry!
it's because the force downwards comes from the magnets - the wire is not actually touching the scale, so any downwards force on the wire would not affect the reading on the scale at all
instead, the scale reading increase comes from the fact that the magnets, which are the ones actually causing the weight on the scale, feel a force downwards
so you need to take the force as upwards because an upwards force on the wire would be accompanied with a downwards force on the magnets
Sorry,I’m still not understanding it. From my thought process before the switch is closed the person had made the scale 0 which removes the weight force from the magnet. When the switch is closed an additional force is acted onto the scale, which is the downward force exerted by the wire onto the magnet resulting to a greater downwards force.
Original post by The A.G
Sorry,I’m still not understanding it. From my thought process before the switch is closed the person had made the scale 0 which removes the weight force from the magnet. When the switch is closed an additional force is acted onto the scale, which is the downward force exerted by the wire onto the magnet resulting to a greater downwards force.
the wire is not actually touching the magnet - as you can see in the diagram, it's suspended between the magnet and the cradle.
the scale was zeroed beforehand, so yes, the weight of the cradle and the magnet was removed, but any additional weight will still come from the magnet's weight increasing - the weight of the magnet doesn't disappear.
the field induced from the current in the wire interacts with the field between the two magnets, and the magnets and wire both repel each other. so while the wire feels a force upwards from the repulsion, and will probably rise into the air a little, the magnets are already on the scale and when they feel a repulsive force downwards, the reading on the scale will increase
you can think of it as putting a bar magnet on a scale with the south pole facing down (for example) and the north pole facing up. If you get another magnet, and push the north pole towards the magnet on the scale, the magnet will feel a repulsion force downwards and its weight will increase, even though the magnet you're holding isn't actually directly touching the scale and adding its own weight.
When u apply FLHR, its on the wire, NOT the magnet. When the scale reading increases, it suggest its “heavier” and thus imply a downward force acts on the magnet. The downward force is due to the wire pushing down the magnet. The magnet will exert an equal force on the wire upwards. (Repulsive force)
Quick Reply
Related discussions
- phyiscs magnetism gcse
- Which Fleming's Hand Rule to Use?
- Physics magnetic fields question
- physics magnetic field question
- Redox question help
- Roundabout
- A level maths help
- Vectors proof
- A level physics magnetic flux question
- Unusual school rules?
- steering to the left when doing a parallel park
- Has anyone been involved in a level malpractice?
- Math question help!
- Chemistry help urgent Alevel
- Was X a rule in your house?
- Using gel pens in exams?
- Can an obsessive guy be faithful?
- Effect of magnetic field on pair prooduction
- A strange teacher
- GCSE Physics AQA Topic 7 (Electromagnetism) I need help!!!
