Physics 9702 · AS & A Level · Equilibrium of forces

Equilibrium of forces — practice question

The diagram depicts two horizontal metal plates that are parallel to each other. A potential difference $V$ exists across the plates. A tiny charged liquid drop is positioned halfway between the plates and remains in equilibrium because its weight is balanced by the electric force on it. The acceleration of free fall is $g$ and the electric field strength is $E$. Determine the polarity of the charge on the drop, and find the ratio of charge to mass of the drop.

  • Anegative, $\frac{E}{g}$
  • Bnegative, $\frac{g}{E}$
  • Cpositive, $\frac{E}{g}$
  • Dpositive, $\frac{g}{E}$

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