right hand grip rule?! (1 Viewer)

[hoca pontis]

ahh!!!
i really dont understand the right hand grip rule ...from physics. its confusing. it really all depends on which way you grip it. is there a definite way of know how to hold it?
i know you grip the wire with your thumb in the same direction as the current, and the force will be perpendicular to that..but what if you turned your fingers facing up instead of down? its still griping the wire with thumb in direction of current, but then the force can be anywhere..
help me...lol

thanks heaps

 

[alcalder]

The right hand grip rule/right hand rule must be done using (obviously) the right hand. It is funny to watch students do physics exams with their pen in their right hand and doing the hand rule with their left hand. They will inevitably end up with the wrong answer. I always tell students - PUT YOUR PEN DOWN then do the hand rules.

Anyway, the rules. They are not too hard to remember. The trick is to hold your hand the right way.

Take your right hand, point your thumb upwards, ie perpendicular to your outstretched fingers. The Thumb is the direction of the conventional current because there is only one wire (and obviously opposite direction to the motion of electrons). The fingers represent the magnetic field because we always draw a mag field with multiple x's or o's. The palm of the hand is the force experienced because we push with our palm.

Now to grip the wire. Hold your hand (thumb perpendiculr to your outstretched fingers) next to the wire. The thumb points up or down the wire (depending on direction of current. The fingers now wrap around the wire. This indicates the direction of the magnetic field. You can't wrap your fingers around the wire any other way unless you can bend your fingers backwards.

The grip rule really only tells you direction of mag field around a current carrying wire. If you want to look at forces on particles in that mag field you use the right hand rule (but in a different way).

Does that clear up the grip rule?

 

[ybnormal]

alternatively, use this different right hand rule. its simpler, and even sometimes our teacher gets the grip one wrong!

your fingers are the magnetic current (easy to remember cos the magnetic current is lots of lines)
your thumb points in the direction of the current
your palm is where the force comes out of.

if u want a diagram pm me

 

[alcalder]

Actually, the grip and right hand rules are exactly the same. It is just that the grip rule does not indicate force because it is used to show the direction a magnetic field circles a current carrying wire.

 

[hoca pontis]

thanks heaps. that kinda clears things up.
one more thing...so the force comes out of the palm..or into the palm?

 

[twilight1412]

out of the palm ... another way of thinking of it is the right hand push rule

f = qv x b

thumb is v
fingers are b
palm is f
you are pushing in the direction of the force

f = il x b
thumb is i
fingers are b
palm is f