Three common electric fields you would apply to a electron.
1. Apply E is the same direction as the velocity
2. Apply E in the opposite direction as the velocity
3. Apply E perpendicular of the velocity
1. The electron will decelerate as the force is opposite to the velocity. The potential applied is known stopping potential in photoelectric effect where the electron come to a stop, KE = eVs.
2.The electron will accelerated as the force is in the same direction as the velocity. The potential applied is know as accelerating potential as seen in Xray tube where the electron of high speed head towards the metal target, KE = eVacc. Electrons are also accelerated this way in CRO tube. Other charges like ions are also accelerated in the mass spectrometer before entering the velocity selector and magnetic filed B region , KE = qVacc.
3. The electron deflect as it moves in this field and the potential is known as deflecting potentials. Projectile motion is observed as the acceleration is in y direction and velocity having x and y components. Acceleration a is often used together with equations of motion to find determine the resultant motion.
