Vacuum tube with screen show cathode rays bent with a magnet.

Vacuum tube with screen shows cathode rays bent with a magnet. An evacuated tube has an anode at one end, a cathode at the other, and a fluorescent screen in between. When a high voltage (about 40 kV pulsating D.C.) from an induction coil is placed across the tube, a beam of electrons is emitted from the cathode, passes through a slit, then travels in a straight line to the anode. When a horseshoe magnet is lowered down over the tube, the beam of electrons is deflected. (By the 'right-hand rule', the direction of the deflection is qVxB. So, the deflection of the beam is down, if the North pole of the magnet is going into the page...) The beam of electrons impinges on the fluorescent screen, making the path of the beam visible. (Same apparatus as X ) Ref.:Modern College Physics by Harvey White, 6th ed., p. 624-628