Electromagnetism is due to the magnetic fields around electric currents. The fields can cause forces with other nearby magnets which can be used to make motors spin. Transformers use electromagnetic induction to change the voltage of alternating currents.

A wire carrying a current creates a magnetic field. This can interact with another magnetic field, causing a force that pushes the wire at right angles. This is called the motor effect.

To calculate the force on a wire carrying a current at right angles to a magnetic field, use the equation:

force = magnetic flux density × current × length

This is when:

*F*is force in newtons (N)*B*is magnetic flux density (magnetic field strength) in tesla (T)*I*is current in amperes – also referred to as amps – (A)- is length in metres (m)

2 A flows through a 50 cm wire. Calculate the force acting on the wire when it is placed at right angles in a 0.4 T magnetic field.

50 cm = 50 ÷ 100 = 0.5 m

- Question
A 5.0 cm wire carries a current of 0.75 A. Calculate the force acting on the wire when it is placed at right angles in a 0.60 T magnetic field.