Flow speed, electric generator, and mass spectrometer: Putting it all together...

Flow speed, electric generator, and mass spectrometer: Putting it all together

An electron moves between two parallel plates, as shown in Figure P17.41. A 480-N/C field points from the upper plate toward the lower plate. A 0.12-T magnetic field points into the paper. (a) Determine the electric force (magnitude and direction) that the electric field exerts on an electron between the plates. (b) At what speed and in which direction (right or left) must the electron move so that the magnetic field exerts an opposing force that balances the electric force? (If narrow slits are placed at the entrance and exit of the plates, the device allows charged particles of only one speed to pass through both slits. Such a device is called a velocity selector.)