RHR for Magnetic fields, why is it design in such a way?

In summary, the right hand rule is a convention that allows us to define our magnetic fields in the same way, regardless of which hand we use.
  • #1
Wek
18
0
I don't feel like this is a homework question, more like a curiosity question. If I'm wrong then feel free to move it to the homework section and my apologies.

I know how the RHR works for magnetic forces and I can apply it with no problem, however I'm not a physics major so maybe I'm missing crucial info. Anyway, my question is why the RHR rule applied the way it is. I mean take a look at this picture about how the railgun works:

http://upload.wikimedia.org/wikipedia/commons/9/9a/Railgun-1.svg

For the projectile line (orange), why do I have to use the RHR (hand upright) in such a way that the force is facing away (towards the left)? I'm not questioning the mechanics of the device, it wouldn't make sense to have the force pointed at you for obvious reasons. But, why would applying the RHR with the hand pointing upside-down (therefore the force directed to the right instead) be wrong?

Thanks
 
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  • #2
The right hand rule is a convention so that we all define our magnetic fields the same way. We could have defined the convention using a left hand rule, as long as in the end the direction of the force stays unchanged. The force is the only thing we can "see", we can't "see" magnetic fields, and it's not like magnetic fields are actually little arrows that point in a certain direction. What we can see is how particles act in magnetic fields. As long as we don't change the equation of motion, it is arbitrary which direction I want to define magnetic fields. If the magnetic fields change direction (so that a current's magnetic field direction is defined by a left hand rule), I merely have to redefine how they act on plus and minus charges (also using the left hand rule).
 
  • #3
I would merely like to add to Matterwave's excellent answer that it's possible (and desirable!) to avoid this arbitrary convention altogether. Instead of visualizing the magnetic field as a vector, pointing in some direction, it can be visualized as a plane with a given orientation (clockwise or counterclockwise). See this puzzle:
http://www.av8n.com/physics/pierre-puzzle.htm
and its solution:
http://www.av8n.com/physics/pierre-answer.htm
for a concise introduction.
 

What is RHR for Magnetic fields?

RHR stands for Right-Hand Rule, which is a method used to determine the direction of a magnetic field in relation to the direction of current flow. It is based on the principle that when a current-carrying wire is placed in a magnetic field, the wire will experience a force perpendicular to both the direction of the current and the direction of the magnetic field.

Why is RHR used to determine the direction of magnetic fields?

RHR is used because it follows the convention of the direction of current flow, which is from positive to negative. This helps to establish a standard method for determining the direction of magnetic fields, making it easier for scientists and engineers to communicate and understand each other's work.

How is RHR applied in real-life situations?

RHR is applied in various real-life situations, such as in the design of electric motors and generators, as well as in the construction of electromagnets. It is also used in medical imaging techniques like magnetic resonance imaging (MRI) and in navigation systems like the compass.

Why is RHR designed in such a way?

RHR is designed in such a way to ensure consistency and accuracy in determining the direction of magnetic fields. With a standard method in place, it becomes easier to compare and analyze data, making it a crucial tool in the study and application of electromagnetism.

Are there any exceptions to RHR for Magnetic fields?

While RHR is the most commonly used method for determining the direction of magnetic fields, it does have some exceptions. In some situations, the direction of current flow or the direction of the magnetic field may be opposite, resulting in a reversal of the direction of the force. However, these exceptions are rare and can be easily identified by understanding the underlying principles of electromagnetism.

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