right hand rule question

[patrickd223]

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Okay, so you point your thumb in the direction of the current and the way your fingers curl is the magnetic field. My question is this: How do you know if that way is CW or CCW, dont they have to give you some kind of reference point to judge from? thanks.

 

[auroraboy]

Okay, so you point your thumb in the direction of the current and the way your fingers curl is the magnetic field. My question is this: How do you know if that way is CW or CCW, dont they have to give you some kind of reference point to judge from? thanks.

In order to consider the magnetic field as CW or CCW you must set a reference frame..for example this could be done by defining current into or out of the plane..that way magnetic field could be defined as CW or CCW in the plane.

hope that helps

 

[physics junkie]

You orient yourself by putting your thumb in the direction of the current flow. If your thumb points up then the current goes CCW(looking from above). If your thumb points down the current goes CW(looking from above). Obviously if you asked a small kid who was below your hand while you did the right hand rule they would tell you the opposite. This is exactly the same as having to specify "your right" or "my right" when telling someone something when you are standing face-to-face with them. CCW or CW depends on whether you're looking at the phenomenon from above or below the plane.

The MCAT shouldn't use such loose terminology. If it does then just consider yourself looking at the computer screen instead of looking from behind(assuming you could see through to the screen from behind).

auroraboy, I think you get it but to clear up your example... Even if you define if the current is coming into or out of the plane you would have to specify in some unambiguous way whether you are (above/below) or (behind/in front of) that plane to say CW or CCW.

 

[TheMightyTexan]

Hey, just ran across a problem like this, 888 in EK physics 1001...just wanted to make sure physics junkies answer was current. I can do most RHR problems, should this be acceptable?