This is derived from $F = BIL$ by substituting $I = Q/t$ and $L = vt$
Electromagnetism - OCR A-Level Physics
$$F = BQv\sin\theta$$
- This is derived from $F = BIL$ by substituting $I = Q/t$ and $L = vt$.
- The magnetic force is always perpendicularAt right angles (90 degrees) to a given line, surface, or direction. to the velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹., so it does no work and cannot change the particle's speed - only its direction.
- For a positive chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C)., use Fleming's left-hand rule with the 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). in the direction of motion. For a negative chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). (e.g. electron), the conventional currentThe rate of flow of charge. Measured in amperes (A).The direction of currentThe rate of flow of charge. Measured in amperes (A). flow defined as from positive to negative. Opposite to the direction of electron flow. is opposite to the direction of motion.
Examiner Tips and Tricks
- Exam questions often ask why the magnetic force does no work on a charged particle.
- The answer: the force is always perpendicular to the displacementThe distance moved in a particular direction from a starting point. A vector quantity. Measured in metres (m)., so W = Fs cos 90° = 0.
- The kinetic energyThe capacity to do work. Measured in joules (J).The energyThe capacity to do work. Measured in joules (J). an object possesses due to its motion. and speed remain constant.