Physics 9702 · AS & A Level · Equilibrium of forces

Equilibrium of forces — practice question

A steady potential difference is maintained across two horizontal metal plates. An electrically charged oil droplet is kept stationary by the electric field between the plates. When part of the oil evaporates, the droplet’s mass decreases and it begins to accelerate. Its charge stays the same. In which direction will the droplet accelerate, and what change must be made to the separation of the plates to stop this acceleration?

  • Adirection of acceleration: downwards; separation of the plates: decrease
  • Bdirection of acceleration: downwards; separation of the plates: increase
  • Cdirection of acceleration: upwards; separation of the plates: decrease
  • Ddirection of acceleration: upwards; separation of the plates: increase

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