3.7.5.1
Magnetic flux density tells you how strong the field is
Magnetic Fields & Forces — AQA A-Level Physics
Key Definition
Magnetic flux density — The number of magnetic flux lines passing through a region of space per unit area. Symbol: B. Measured in teslas (T).
$$F = BIL\sin\theta$$
Key Definition
The tesla — One tesla (1 T) is the flux density that causes a force of 1 N on a 1 m wire carrying a current of 1 A at right angles to the flux.
- The teslaThe SI unit of magnetic flux density. One tesla is the flux density when a force of 1 N acts on a 1 m conductor carrying 1 A perpendicular to the field. bundles three measurable quantities into one unit: force, currentThe rate of flow of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C).. Measured in amperes (A)., and length. The required practical exploits this directly.
- Where flux lines are bunched closer together, B is higher and the field is stronger.
- Where flux lines spread apart, B is lower and the field is weaker.
Examiner Tips and Tricks
- 'Uniform magnetic field' means B has the same value everywhere in that region.
- The flux lines are equally spaced and parallel.
- Most exam questions assume a uniform field unless told otherwise.