A-LevelPhysicsElectric fields9702/12 · May/June 2015 · Q301 Mark
A charged oil drop of mass m, with n excess electrons, is held stationary in the uniform electric field between two horizontal plates separated by a distance d. [Figure showing two parallel plates, connected to a voltage V. An oil drop with mass m and charge q is between them. Field lines point up (from negative to positive plate).] The voltage between the plates is V, the elementary charge is e and the acceleration of free fall is g. What is the value of n?
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
AeV / mgd
Bmgd / eV
CmeV / gd
Dgd / meV
✓ Correct answer
B: mgd / eV
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