Direction of Magnetic Field

[qw098]

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Hi,

How do I know for the picture below the direction of the Magnetic Field?

Once I know the direction of the magnetic field I can use the RHR (Right-Hand rule) to determine the direction of the Magnetic force. For b) and c) the direction of the magnetic field is not shown (is the magnetic field putting out of the page or into the page!?) so I am not sure how to figure out the direction of the magnetic force.

For a) and d) the direction of the magnetic field is drawn as arrows so it is easy.

If someone can help me that would be great!

 

[milski]

It's matter of convention. The circle with the dot means that the direction of the field is out of the page, towards you, the x mark - into the page. The logic is that the you're looking at an arrow - the circle with the dot represent the head of the arrow, the cross mark - the tail.

 

[qw098]

It's matter of convention. The circle with the dot means that the direction of the field is out of the page, towards you, the x mark - into the page. The logic is that the you're looking at an arrow - the circle with the dot represent the head of the arrow, the cross mark - the tail.

Ah, love it!

Thanks!

 

[Singhp03]

answer to this problem is A i believe, with the mag field down and velocity to the left, the result force vector is out of the page(right hand rule). correct me if am wrong

 

[qw098]

answer to this problem is A i believe, with the mag field down and velocity to the left, the result force vector is out of the page(right hand rule). correct me if am wrong

Yes, you're correct. I got the answer correct as well. I was lucky that the correct answer at the time didn't include the diagram with the "x" and "o" 🙂