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Electric Charges and Fields
Question
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In a discharge tube ionization of enclosed gas is produced due to collisions between

  • positive ions and neutral atoms/molecules

  • negative electrons and neutral atoms/molecules

  • photons and neutral atoms/molecules

  • neutral gas atoms/molecules

Answer

B.

negative electrons and neutral atoms/molecules

In a discharge tube, after being accelerated though a high potential difference the ions in the gas strike the cathode with huge kinetic energy. This collision liberates electrons from the cathode. These free electrons can further liberate ions from gas molecules through collisions. The positive ions are attracted towards the cathode and negatively electrons move towards anode. Thus, ionization of gas results.

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Some More Questions From Electric Charges and Fields Chapter

a) An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not?
b) Explain why two field lines never cross each other at any point? 

Figure shows tracks of three charged particles in a uniform electrostatic field. Give the signs of the three charges. Which particle has the highest charge to mass ratio?