Question

1. An electron moving with as initial speed of 2.85 x 10' m/s encounters a stopping potential That is, the electron is stopped by a potential difference AV«. a) Find the potential difference required to stop the electron. b) The electron stops in 3.00 m, find the magnitude of a constant electric field associated with the stopping potential c) Would a proton travelling at the same speed require a greater or lesser magnitude potential difference to stop? Explain d) Find a symbolic expression for the ratio of the electron to the proton stopping potentials AVp/AVe. The answer should be in terms of the proton mass m, and the electron mass m..

Answer 1

- 1.6810-19 mass g electron me = 9.11X10%' kg Charge of election 20 = 1.681019cº Initial speed V = 2.85*10* mis Let the potential difference be Ave from the law of conservation of energy kinetic energy - Potential energy Amen? = qe Ave >> Ave = 4 me - 0. * £* 9:1810**2-85 x103) = 23124 v 6) Alo Aves Ed E = AV for d=3m E = 2312-4 = 770.8 Vim (c) mp = 1.67X1024 kg , 9p = t·b X10"C (29e) potential dijzerence svp = į movie - © = { x 1 47810*x (2.65 x103) = 42.39x105, Clearly aUp) Ave Both have same change but mp) me and hence KEp> KEO (6) Dividing eq= ② by @, we get