Microscopic dust particles often acquire electric charge while drifting through…
PHYSICS · Multi-part · CBSE · Physics · Electric Charges and Fields · Electric Charges and Fields
Problem
Microscopic dust particles often acquire electric charge while drifting through Earth’s atmosphere. Consider a spherical dust grain of mass 3.2×10−12kg that acquires n additional electrons, giving it a net charge of q=ne.
The dust grain enters a region where a uniform downward electric field of magnitude 15kNC−1 exists. Neglect air resistance.
(a) For n=300 extra electrons on the grain, calculate its net charge.
(b) Determine the magnitude and direction of the electric force acting on the grain for the charge found in part (a).
(c) Compare the magnitude of the electric force with the gravitational force on the grain. State which force dominates and justify your answer quantitatively.
(d) If instead the electric force is required to exactly balance the grain’s weight, determine the number of excess electrons the grain must carry.