EK Magnetic Field & Electric no. 165

[SaintJude]

View attachment 18714

What direction should the magnetic field be in?

And using the right hand palm rule, can you include what direction your thumb, palm, fingers are pointing to?

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[rowjimmy]

Pick a charge for the droplet. Let's just say it's positive. When if starts to fall it will be attracted to the negative plate so it will start to fall to the right. In order to counteract this a magnetic field can be applied and it is the magentic filed force that will be able to change the direction of the droplet's movement. So in the RHR the palm is this force and your thumb is the direction of the charge. So pointing your thumb downward and palm pointing to the left (remember we want to counteract the electric field force which is to the right) we notice that the fingertips (magnetic field) point out of the page.

Note you can do this over with a negative charge and arrive at the same result-- but just remember to reverse the end result because the RHR is for orientations of positive charges. Negative charges will have opposite results. Thus if the negative charge is in that e field it will go towards the left. In order to make it go right the palm of your hand should point right and thumb downward. The fingertips point into the page (for a positive charge) and reverse that for a negative charge and you arrive at a magnetic field that is out of the page, same as before.

I just noticed that you can use your left hand for negative charges and dont have to reverse the end result. Someone correct me if I am wrong. This would be GROUNDBREAKING for me because I always forget to reverse the end result for negative charges.

 

[SaintJude]

Haha-Rowjimmy--your groundbreaking discovery is true! Glad, you helping me, helped you.

I think what I got hung up on was that I didn't recall that it's the force that determines the direction of the acceleration. But def should have realized this since one of the 1st lessons in newtonian physics is acceleration is in the direction of net force. Thanks!