# Homework Help: Magnetic Fields

1. Oct 23, 2011

### Physics Help!

Please help me with these choose the best answers since I'm not sure of my answers.

A current element produces a magnetic field in the region surrounding it. at any point in space, the magnetic field produced by this current element points in a direction that is
a) radial from the current element to the point in space.
b) parallel to the current element;
c) perpendicular to the current element and to the radial direction.

I think it's c.

the magnetic force cant do work on a charged particle since the force is always perpendicular to the velocity. How then can magnets pick up nails? Consider two parallel current carrying wires. The magnetic fields cause attractive force s between the wires so it appears that the magnetic filed due to one wire is doing work on the other wire. How is this explained?
a) the magnetic force can do no work on isolated charges; this says nothing about the work it can do on charges confined in a conductor.
b) since only an electric field can do work on charges, it is actually the electric field doing work here.
c) This apparent work is due to another typo of force.

I pick c again.

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