6.12 understand that a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers

If a current through a piece of wire is held at right angles to a magnetic field, the wire will move (as a force is created)

When a current flowing through a wire is put through a magnet, the magnetic field lines overlap. 

in some places, the direction of the fields are the same, and the magnetic field is stronger. in other places, the direction of the fields are in opposite directions, so the magnetic field is weaker. 

the wire is pushed from the strong part of the field to the weak part (the magnetic field lines don’t like being squished together) 

electric motors

the magnets on the two sides of the coil are at different directions. One side feels the force pushing it downwards, whilst the other is being pushed upwards, so the coil rotates. 

the direction current on each side of the coil is switched when the coil is vertical by the commutator, so the forces acting on each side is switched and the rotation direction is maintained 

to increase rate of motor turns:
- increase the number of turns or loops of wire (to make a coil)
- increase the strength of the magnetic field
- increase current flowing through the loop of wire 

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