To understand how the two factors affect the force, we can use a concept called Fleming's left-hand rule.

Using your left hand, this rule involves:

• Point your index finger forward – This represents the direction of the magnetic field, pointing from the north to the south pole.
• Extend your middle finger to the side – This represents the direction of the current.
• Point your thumb upward – The direction your thumb points indicates the direction of the force felt by the wire.
• Each direction is 90° to each other
• Use this to work out the unknown factor out of the three (usually the direction of the force felt)
• Remember current is conventional current, which moves in the opposite direction to the electrons

Formula

• $F$ = force in newtons (N)

• $B$ = magnetic flux density in tesla (T)

• $I$= Current in amperes (A)

• $L$ = Length in metres (m) Where Magnetic Flux Density is measured in Tesla

• And it is the number of flux lines per metre squared