# Physics help ! :)?

Im pretty good at physics but this topic confuses me ! It’s electromagnetism. I understand Flemings left hand rule okay enough but I’m stumped on what most people would find easy 1 markers !

1- what do arrows on a magnetic field represents?

2-what effect would changing the direction of the current have on the magnetic field ?

If anyone could help that would be fab ! :)

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• The magnetic field lines originate from the north pole. Arrow denotes the north pole. The electric field changing does add to the magnetic field. If it changes in a coil, then the magnetic field is created. This add to the magnetic field. If it is a wire, then the magnetic field is created perpendicular to the current direction. If the current flow is along the z axis then the magnetic field will be in the x y plane and components point toward positive x and y axis.

• A compass is a bar magnet. When this is placed in a magnetic field it rotates ( a torque is applied by the field ) UNTIL it lines up with the field.

The direction that the compass points is the direction of the field AT THAT POSITION.

Clearly at different positions the compass points in different directions.

The LOCUS of a series of these points creates what you know to be a "magnetic field line ( or curve ).

If you change the direction of the current then the field CAUSED BY THAT CURRENT will reverse in direction. ( at any given point in space ).

• 1) Each arrow represents the direction of the magnetic field; if you could have an isolated north magnetic pole (you can't!) the arrow would tell you the direction of the force on the pole.

2) Changing the current direction reverses the direction of the magnetic field (each arrow would point in the opposite direction).

• Aimee8 months agoReport

Thank you so much !!!!!!!!!

• Arrows in physics typically signify a vector of some sort. And means something that has both direction and magnitude.

1. For the magnetic field the tiny arrows show the direction of the magnetic field, typically signified as the B field (E field for the electric half of EM field).

Those arrows have no real meaning until they are examined in relation to an electrical charge, q. When a charge, q, is passed through the B field (or the B field is passed over it) a force F is produced while there is motion v. And the direction of that force is found from F = q(v X B) for a point charge q moving with velocity v through the B field.

v X B = vB sin(theta) is a cross product. And the direction of that cross product follows the right hand rule (i.e., with the right hand curl you fingers in the direction v to B and the thumb will point to the direction of the cross product result). In the special case when the charge passes through B at a right angle theta = 90, we have F = qvB for the force produced.

Bottom line those B arrows show the direction of the field and that can be used to determine to find the direction of a force created on a charge moving through that field.

2. 1. was a bit long, but now I can shorten this answer. Note F = qvB. If we change the direction of the current here, we make the v become -v, a 180 deg change in the direction of the velocity. And there we are with the change in current direction (which is the motion of electrons, lots of q's with velocities v) we change the direction of the force result F to minus F, -F. In a practical experiment, if your EM magnet has a north pole on one end it when passing a current through its coil, the north pole will switch to the opposite end if you reverse the current through the coil around the magnet.

• Aimee8 months agoReport

Thank youuuuuu !