Force on a current carrying conductor placed in magnetic field $B$ If I place a thin current carrying conductor (electric current=i)in a magnetic field, the force acting on it is F=i(lXB). I have a doubt.
Is B the external magnetic field or the vector sum of the external magnetic field and magnetic field produced by it?
 A: Force on the conductor due to external magnetic field only. Do you mean the field due to change in current in the conductor...... That's different thing .induced magnetic field cannot exert force on conductor from which it is produced like as electric field can't exert force on a charge due to which field is produce. 
A: External. Magnetic field produced by current in conductor cannot exert a force on conductor. Use right hand thumb rule to see direction of magnetic field induced by current.
Let's say we have a current carrying rod, using right hand thumb rule we see magnetic field exists in circular loops perpendicular to current. In order to exert a force we need B x v. Inside the conductor the direction of magnetic field cannot be defined because it will be a circle with radius 0. Therefore, current induced magnetic field does not exert force on rod.
A: A charged particle in motion experiences a magnetic force in a magnetic field.Similarly,a current carrying wire also experiences a force when placed in a magnetic field.This is because the conductor is made from a collection of charged particles.Hence the force exerted by wires is transmitted to the wire when the particles collide with the atom making the wire since they can't escape from the conductor

