direction parallel = 90o = current direction perpendicular to F Fmax magnetic field direction p1.34 p1.44 = 1.2310-3 T = 22.5 m = 2.2510-3 m B d accelerating voltage = 10.5 kV = 10.5103 V Va (a) = ? m.s-1 v accelerating voltage does work on the electron increasing its kinetic energy (b) hand screw rule magnetic force directed up the page – (c) magnetic force & electric force must cancel electric force directed down the page – (d) Electric field between the plates same direction as force on a positive charge – up the page – (e) voltage across the plates bottom plate is positive (electron attracted to bottom plate) – (f) J.J Thompson’s e/m experiment From measurement of (or and and the can be found. E V d), B Va e/m Alternatively: Thomson adjusted the electric field strength and magnetic field strength to make the electrons pass straight through. This allowed him to calculate the velocity of the v electrons (cathode rays). He then passed the electrons through the magnetic field alone, and B from the radius of their path calculated the q/m ratio R p1.65 (a) striations (b) right hand side is the cathode striations are nearer than anode – (c) See notes Electrical discharges (d) Pattern will not significantly change but molecules of different gases emit radiation of different frequencies in such transitions. Therefore, the glow of the positive column has a characteristic colour for each gas. (e) The pressure of the gas is mainly responsible for the observed patterns.
direction parallel = 90o F = Fmax current direction perpendicular to magnetic field direction p1.34 p1.44 B = 1.2310-3 T d = 22.5 m = 2.2510-3 m accelerating voltage Va = 10.5 kV = 10.5103 V (a) v = ? m.s-1 accelerating voltage does work on the electron increasing its kinetic energy (b) hand screw rule – magnetic force directed up the page (c) magnetic force & electric force must cancel – electric force directed down the page (d) Electric field between the plates – same direction as force on a positive charge – up the page (e) voltage across the plates – bottom plate is positive (electron attracted to bottom plate) (f) J.J Thompson’s e/m experiment From measurement of E (or V and d), B and Va the e/m can be found. Alternatively: Thomson adjusted the electric field strength and magnetic field strength to make the electrons pass straight through. This allowed him to calculate the velocity v of the electrons (cathode rays). He then passed the electrons through the magnetic field B alone, and from the radius R of their path calculated the q/m ratio p1.65 (a) striations (b) right hand side is the cathode – striations are nearer than anode (c) See notes Electrical discharges (d) Pattern will not significantly change but molecules of different gases emit radiation of different frequencies in such transitions. Therefore, the glow of the positive column has a characteristic colour for each gas. (e) The pressure of the gas is mainly responsible for the observed patterns.
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