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Two plates are kept at a distance of 0.1m and their potential difference is 20V. An electron is kept at rest on the surface of the plate with lower potential. What will be the velocity of the electron when it strikes another plate?
  • a)
    1.87*106 m/s
  • b)
    2.65*106 m/s
  • c)
    7.02*1012 m/s
  • d)
    32*10-19 m/s
Correct answer is option 'B'. Can you explain this answer?
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Two plates are kept at a distance of 0.1m and their potential differen...
Given data:
Distance between two plates (d) = 0.1m
Potential difference between two plates (V) = 20V

To find: Velocity of electron when it strikes another plate

Formula used:
The potential difference between two plates is given by: V = Ed
where E is the electric field between the plates and d is the distance between the plates.

The electron placed at the lower potential plate has potential energy (PE) given by:
PE = qV
where q is the charge of the electron and V is the potential difference between two plates.

The potential energy of the electron is converted into kinetic energy when the electron moves towards the higher potential plate. The kinetic energy of the electron is given by:
KE = 1/2mv^2
where m is the mass of the electron and v is the velocity of the electron.

As per conservation of energy, the potential energy of the electron is converted into kinetic energy. Therefore,
PE = KE
qV = 1/2mv^2

Solving for v, we get:
v = sqrt(2qV/m)

Substituting the given values, we get:
v = sqrt(2*1.6*10^-19*20/9.1*10^-31)
v = 2.65*10^6 m/s

Therefore, the velocity of the electron when it strikes another plate is 2.65*10^6 m/s.

Answer: Option B.
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Community Answer
Two plates are kept at a distance of 0.1m and their potential differen...
Increase in potential energy of the electron when it strikes another plate = Potential difference*charge of electron=20*1.6*10-19 J=3.201*10-18J and as the electron was at rest initially, this energy will be converted to kinetic energy completely. Therefore, 0.5*mass of electron*(velocity)2=3.201*10-18J. Substituting m=9.11*10-31kg, we get v=2.65*106 m/s.
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Two plates are kept at a distance of 0.1m and their potential difference is 20V. An electron is kept at rest on the surface of the plate with lower potential. What will be the velocity of the electron when it strikes another plate?a)1.87*106m/sb)2.65*106m/sc)7.02*1012m/sd)32*10-19m/sCorrect answer is option 'B'. Can you explain this answer?
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