A straight wire is placed at right angles to a uniform magnetic field.
The length of wire in the magnetic field is 5.0 cm.
The magnetic flux density is 0.20 T0.20\ \text{T}0.20 T and the current in the wire is 3.0 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 force on the wire.
The wire is turned so that it lies parallel to the magnetic field.
State the size of the force on the wire now.
The wire is turned back so that it is at right angles to the magnetic field.
The current is doubled and the magnetic flux density is halved.
State the size of the force on the wire. Give a reason for your answer.
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.