Answer to Question #258871 in Electricity and Magnetism for K-Lo

Question

A charged dust particle with a mass of 8.48 (10-15) kg is suspended between two horizontal charged plates subject to a 240 V electric potential difference. [4T]

a) Create an FBD (free-body diagram) for the dust particle.  Label all forces, including magnitudes.

b)The dust particle was charged due to friction, which caused electrons to be removed from the particle.  Determine how many electrons were lost due to the friction, creating the charge on the particle.

Answer 1

$F_g=F_e,$

$mg=\varphi\frac qd,$

$q=ne,$ $\implies$

$n=\frac{mg}{\varphi e}=2200.$