When a conductor carrying a current is placed in a magnetic field, the conductor experiences a magnetic force.

- The direction of this force is always right angles to the plane containing both the conductor and the magnetic field, and is predicted by Fleming’s Left-Hand Rule.

Diagram by Jfmelero. Link: http://en.wikipedia.org/wiki/File:ManoLaplace.svg. Available under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Referring to the diagram above, F is Force, B is Magnetic field, I is current.

Factors affecting magnetic force on a current-carrying conductor in a magnetic field:

- Strength of the magnetic field
- Current flowing through the wire
- Length of the wire

$F = B I l \, sin \, \theta$, where

- F is force acting on a current carrying conductor,B is magnetic flux density (magnetic field strength),
- I is magnitude of current flowing through the conductor,
- $l$ is length of conductor,
- $\theta$ is angle that conductor makes with the magnetic field.

When the conductor is perpendicular to the magnetic field, the force will be maximum. When it is parallel to the magnetic field, the force will be zero.

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Why is sin theta used instead of cos theta when talking about the angle between B and L?

Because force is a the resultant of B and L is Force which is a vector quantity.

Can you explain it to me

Drive an expression for the magnitude of the force in a current-carry conductor in a magnetic field.

What will be the affect on the magnetic force if we double all the parameters keeping sin 90°?

The force on current carrying wire is due to applied magnetic field or its own magnetic induction?

the external and internal b field interact which result in a magnetic force on a conductor.

Why does a solenoid contract when a current is passed through it ?

Because of magnet

can you give a brief explanation

This depends on the way winding is done in the solenoid, loosely wound conductor in the presence of magnetic attract each other and act as one current carrying conductor.