Deflection

• When charged particles move through a uniform magnetic field, a force will act on them, which can be calculated using F=Bqv sinθ.
• The motion of the particle and the force are always perpendicular to each other, causing the charged particle to move in a circular path.
• Using your understanding of centripetal acceleration, the magnetic force can be equated to the centripetal force and the following equation can be used to calculate the radius of the path of the charged particle: Bqv=rmv2.
• If the moving particles are negatively charged, the direction of current is opposite the direction of the movement.
• When charged particles move through a uniform electric field, such as between two parallel plates, a force will act on them, which can be calculated using F=qE.
• As E=dV for a parallel plate, this can be written: F=qdV.
• The direction of the force will depend on the field, but the direction of motion of the charged particle will not affect the direction of the force.
• When the force is at right angles to the motion, such as in the example below, the acceleration due to the electric field does not change the horizontal velocity but will cause a vertical acceleration.
• The acceleration could be calculated using Newton’s second law; F=ma.
• The particle will obey the same laws of motion as described in unit 1, and the same equations can be used to calculate the horizontal and vertical distance travelled as in projectile motion.
• When the force and motion are in the same direction, the particle will gain kinetic energy as it is accelerated by the electric field.
• The kinetic energy gained by the charged particle moving between a potential difference, V, is ∆KE=qV.
• Where q is the charge of the particle.
• Like poles repel while unlike poles attract.
• A magnet has two poles, north (N) and south (S).
• Magnetic fields have both magnitude (strength) and direction.
• A magnetic field is created around any current carrying wire or conductor.