The magnetic field lines of a long current-carrying wire are concentric circles in the plane perpendicular to the wire. The direction of the field is determined by the right-hand rule.

If the wire is horizontal and the current is to the left, then the magnetic field will be directed into...

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The magnetic field lines of a long current-carrying wire are concentric circles in the plane perpendicular to the wire. The direction of the field is determined by the right-hand rule.

If the wire is horizontal and the current is to the left, then the magnetic field will be directed into the page at a point above the wire and out of the page at a point under the wire (please see the attached image).

The magnitude of the field at a point distance *r* away from the wire is

`B = (mu_o*I)/(2*pi*r)`

Here, `mu_0` is the magnetic permeability of vacuum and is `mu_0 = 4*pi*10^(-7) T*m/A`

For the current of I = 2.1 A and the distance r = 3 m, the magnitude of the field is

`B = (4*pi*10^(-7) * 2.1)/(2*pi*3) = 1.4*10^(-7) T`

The magnetic force on the moving charge can be found as

`vec F = q*vec v xx vecB`

Since the charge is positive and is moving to the right, and the magnetic field is pointing into the page, the direction of the force, as determined by the right-hand rule, will be upward. (Again, please see the attached image.) The magnitude of the force will be

`F = qvB = 1*4250*1.4*10^(-7) = 5.95*10^(-4) N`

See the reference link below discussing the magnetic field of currents and illustrating the right-hand rule.

**Further Reading**