A tiny spherical oil drop carrying a net charge q is balanced in still air, with a vertical uniform electric field of strength 
. When the field is switched off, the drop is observed to fall with terminal velocity 
. Here 
. Viscosity of air is 
and the density of oil is 
. The magnitude of ' q ' is
A
B
C
D
Text Solution
Verified by ExpertsThe correct answer is:
D
Here,
,
When drop is balanced in still air under the effect of electric field, then 
or 
When the electric field is switched off, let the drop falls with terminal velocity v, then
On solving we get, 
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