# what is the direction of magnetic force B?

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#### supertrooper66

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is it in/out of the page or CW/CCW?

with F=qvXB, they always draw the B direction as in/out of page
with a current carrying wire, they draw B as a CW/CCW direction.

which is correct?

#### ballofnerves

##### Full Member
10+ Year Member
is it in/out of the page or CW/CCW?

with F=qvXB, they always draw the B direction as in/out of page
with a current carrying wire, they draw B as a CW/CCW direction.

which is correct?

The direction of the magnetic field B due to a current-carrying wire depends on the direction in which the current is flowing. To determine the direction of the magnetic field, pretend you are grabbing the wire with your thumb pointing in the direction of the current. The direction in which your fingers curl will give the direction of the magnetic field. This is commonly referred to as the right hand rule (RHR) for current-carrying wires.

For the magnetic force B, the direction of the force depends on the direction of the magnetic field, the charge (negative or positive), as well as the direction of motion of the object that is experiencing the force. The direction of force will be perpendicular to BOTH the direction of motion and the direction of the magnetic field. There are other RHRs that are designed to determine the direction of this force. It is difficult to describe without a diagram, so I recommend you look that up somewhere else.

#### supertrooper66

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The direction of the magnetic field B due to a current-carrying wire depends on the direction in which the current is flowing. To determine the direction of the magnetic field, pretend you are grabbing the wire with your thumb pointing in the direction of the current. The direction in which your fingers curl will give the direction of the magnetic field. This is commonly referred to as the right hand rule (RHR) for current-carrying wires.

For the magnetic force B, the direction of the force depends on the direction of the magnetic field, the charge (negative or positive), as well as the direction of motion of the object that is experiencing the force. The direction of force will be perpendicular to BOTH the direction of motion and the direction of the magnetic field. There are other RHRs that are designed to determine the direction of this force. It is difficult to describe without a diagram, so I recommend you look that up somewhere else.

......yes, i know how to find it in both circumstances.

i'm not asking how to find it. i'm asking if the direciton is Clockwise/Counter-clock wise or instead in a linear direction? When you curl your hand around the wire, your hand is curling in a CW/CCW direction. When you are using the RHR with the force, you actually use B as a linear direction. That is what I am confused.

Help?

#### unsung

##### Full Member
10+ Year Member
......yes, i know how to find it in both circumstances.

i'm not asking how to find it. i'm asking if the direciton is Clockwise/Counter-clock wise or instead in a linear direction? When you curl your hand around the wire, your hand is curling in a CW/CCW direction. When you are using the RHR with the force, you actually use B as a linear direction. That is what I am confused.

Help?

I see what you're asking. In problems where the B field is given as just coming out of or into the page, that's like a localized section. For example, imagine the B field directly on top of a current carrying wire that's going into the page. Use your Rhand rule, with your thumb pointing into the page, and it's clear that the B field right on top is pointing to your right, right? So for that point in space, the B field is "linear" not really the right term, but I think you see what I mean.

But that's just for that point in space. If you pull back, then the B field lines are circular, pointing from N pole to S pole always. Also, note you can't isolate either pole- if you cut the magnet in half, you get two small magnets, so that the B field lines still are curved, pointing from N to S.

Does that help?