The motor effect - - - - + + + + When a current carrying wire is placed in a magnetic field, it will experience a force. This is called the motor effect. S + - + - + - N + -

Magnetic Force on a Current-Carrying Conductor Graphics from Ted Vittitoe

Right hand ‘Slap’ rule fingers ~ field Thumb ~ current Slap – force direction

The left-hand motor rule Note: Magnetic field direction is from NORTH to SOUTH Current direction is from PLUS to MINUS

The force increases if: – the strength of the magnetic field is increased – the current is increased The direction of the force is reversed if either the direction of the current or the direction of the magnetic field is reversed. The conductor will not experience a force if it is parallel to the magnetic field. Motor effect - Fendt

Force on an Electric Current in a Magnetic Field A current-carrying wire in a B-field wire experience a Force

dot is coming out of the page cross is going into the page

A Force occurs due to the combination of magnetic fields

 + = neutral point

Insert the missing information Q1. Force direction ? Q2 Current direction ? N S S N Q3 N and S poles ? Q4 Force directions ? N S N S Note: means current out of the page means current into the page

Find the magnitude and direction of the current that must flow through the red bar in order to remove the tension from the springs. x B = .440 T L L = 62.0 cm m = 13.0 g