A tiny spherical oil drop carrying a net charge q is balanced in still air with a vertical uniform electric field of stength 81pie/7 *10^5 V/m. when the field is switched off , the drop is observed to fall wth terminal velocity 2*10^-3m/s. given g=9.8m/s^2, viscocity of the air = 1.8*10^-5Ns/m^2 and the density of the oil =900kg/m^3. the magnitude of q=?
A)1.6*10^-19C
B)3.2*10^-19C
C)4.8*10^-19C
D)8.0*10^-19C

Question

A tiny spherical oil drop carrying a net charge q is balanced in still air with a vertical uniform electric field of stength 81pie/7 *10^5 V/m. when the field is switched off , the drop is observed to fall wth terminal velocity 2*10^-3m/s. given g=9.8m/s^2, viscocity of the air = 1.8*10^-5Ns/m^2 and the density of the oil =900kg/m^3. the magnitude of q=?
A)1.6*10^-19C
B)3.2*10^-19C
C)4.8*10^-19C
D)8.0*10^-19C

nirmalnema · Answer

$$qE=4/3 \pi*r^3*\rho*g$$

nirmalnema · Answer

when the drop descends with constant velocity v in the absence of electric field, then
mg = $$4/3π∗r3∗ρ∗g=6*\pi *\eta*r*v$$

nirmalnema · Answer

from here
$$r^2=(9/2) *(v*\eta/\rho*g)$$

nirmalnema · Answer

from here calculate r
=3/7 * 10^-5

nirmalnema · Answer

$$6∗π∗η∗r∗v = qE            $$

nirmalnema · Answer

$$(6∗π∗η∗r∗v)/E=q$$

nirmalnema · Answer

=8.0*10^-19C

nirmalnema · Answer

ab values dal kar calculate kar lena ans yahi aye ga
may be mera to yahi aya hai

aayushi.somani · Answer

okay thanks :)

nirmalnema · Answer

welcome..!! :)