Magnetic force on a current carrying wire

In summary, the formula for finding the force on a current carrying wire is F=BIL, where F is force, B is the strength of the magnetic field, and L is the length of the wire. This formula does not factor in the distance between the magnet and the wire because it assumes the magnetic field is uniform over the entire length of the wire. However, this is not likely to be true for a real magnet and wire, so the value of B near the magnet should not be used in the calculation for a wire at a long distance.
  • #1
pantheid
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Hi, I am slightly confused by the formula for finding the force on a current carrying wire. It is given as F=BIL where F is force, B is the strength of the magnetic field and L is the length of the wire being acted upon. What I don't understand is why this formula doesn't factor in the distance between the magnet and the wire itself.
 
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  • #2
pantheid said:
Hi, I am slightly confused by the formula for finding the force on a current carrying wire. It is given as F=BIL where F is force, B is the strength of the magnetic field and L is the length of the wire being acted upon. What I don't understand is why this formula doesn't factor in the distance between the magnet and the wire itself.

The magnetic field B is taken to be the field present at the wire itself. Any position dependence of B must be known in order to know the field at the wire. So, yes a far aways magnet will have less force on the wire, but it will also present less magnetic field to the wire. You would not want to use the value of B near the magnet in the calculation of force on a wire a long distance away.

Note that this formula is a simplification that assumes the magnetic field is uniform over the entire length of the wire, which is not likely to be true for a real magnet and a wire of any appreciable length.
 
  • #3
The usual arrangement for demonstrating this involves using a pair of bar magnets (using the gap between a N and opposing S pole), or else a horseshoe magnet, and this arrangement makes the field in that region approximately uniform.
 

1. How does a current carrying wire produce a magnetic field?

When an electric current flows through a wire, it creates a circular magnetic field around the wire. This is due to the movement of the charged particles (electrons) in the wire, which creates a magnetic field according to Ampere's law.

2. How is the strength of the magnetic field related to the current in the wire?

The strength of the magnetic field is directly proportional to the amount of current flowing through the wire. This means that the stronger the current, the stronger the magnetic field will be.

3. How does the direction of the magnetic field change with the direction of the current?

The direction of the magnetic field around a current carrying wire follows the right-hand rule. If you point your right thumb in the direction of the current, your fingers will curl in the direction of the magnetic field.

4. How does the length of the wire affect the magnetic force?

The length of the wire has no direct effect on the magnetic force. However, a longer wire will have a greater amount of current flowing through it, which will result in a stronger magnetic field and therefore a greater magnetic force.

5. Can the magnetic force on a current carrying wire be increased?

Yes, the magnetic force on a current carrying wire can be increased by increasing the current or by using a stronger magnet. The distance between the wire and the magnet can also affect the strength of the magnetic force.

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