Circular Loops of current

[GRod18]

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Do you guys just memorize where magnetic field points in circular loops with current going around in a circle? I can't seem to get right hand rule to work for it.


For example for CCW current, B field points out of the page inside the loop and points into the page outside the loop.

For CW current its the opposite.

Do you guys just memorize this fact?

 

[Rabolisk]

No. I pick a point in the wire. Then I point my thumb in the direction of the current. Then I loooooooop around with the rest of my hand.

Let's say you have a CCW current. Go to the rightmost point in the circle. Stick your thumb pointing up. Stretch out your fingers perpendicular to this thumb (make an L with your thumb and fingers). Now rotate your hand about your thumb. That is the direction of the magnetic field.

 

[vsl5]

Do you guys just memorize where magnetic field points in circular loops with current going around in a circle? I can't seem to get right hand rule to work for it.


For example for CCW current, B field points out of the page inside the loop and points into the page outside the loop.

For CW current its the opposite.

Do you guys just memorize this fact?

Try to visualize it. This annoyed me too when I first learned it, but its really NOT that hard. Do not over think this.

For the CCW current, lets work with the bottom of the loop going left.

So point your thumb left in the direction of the current and wrap your hand around the wire. You'll notice that when you do this, your fingers will be coming out of the page as they bend and the position of your fingers would be inside the loop at this point since they have not curled all the way around. When you curl all the way around, your fingers will have to go back into the page (otherwise you wouldnt be wrapping around the wire). At this point, the fingers will be outside the wire loop going into the page.

If you dont get this, repeat this with a pen. Imagine the pen being the wire with current going in the direction of the pen (CCW or CW, doesnt matter). With this scenario, you can only imagine part of the loop since a pen is straight.

 

[GRod18]

alright thanks a lot to the both of you!!!

ah I get it so its pretty much the same as on a straight wire. Man lol, I don't think prof ever went over this in physics 2. Pretty sure it was one of those things that he crammed in right before finals that was never tested on lol..