A rectangular coil in an electric motor has 50 turns of wire. The coil sits between the poles of a magnet, with the plane of the coil parallel to the magnetic field.
Each of the two sides of the coil that are at right angles to the magnetic field is 4.0 cm long.
The magnetic flux density is 0.30 T0.30\ \text{T}0.30 T and the current in the wire of the coil is 1.5 A.
Use the equation: force=magnetic flux density×current×length\text{force} = \text{magnetic flux density} \times \text{current} \times \text{length}force=magnetic flux density×current×length
Calculate the total force on one side of the coil.
Explain why the forces on the two sides of the coil make it rotate instead of moving it sideways.
The coil turns until its plane is at right angles to the magnetic field.
Forces still act on the two sides of the coil, but they no longer produce a turning effect.
Suggest why.
48 exam-style questions on OCR GCSE Physics 4.2 Uses of magnetism, covering 4.2.1 The motor effect, 4.2.2 Fleming's left-hand rule, 4.2.3 The force on a current-carrying conductor, 4.2.4 The electric motor, 4.2.5 Electromagnetic induction, 4.2.6 Alternators and dynamos, 4.2.7 How transformers work, 4.2.8 Transformer turns ratio, 4.2.9 Potential differences and turns in transformers, and 4.2.10 Microphones, loudspeakers and headphones. Each one has a worked solution and a mark scheme showing where the marks go.