A small charged sphere is attached to a thread and placed in an electric field.
ID: 1872397 • Letter: A
Question
A small charged sphere is attached to a thread and placed in an electric field. The other end of the thread is anchored so that the sphere is in a static situation when placed in the field. If the thread is horizontal, find the magnitude and direction of the electric field. The sphere has a mass of 0.05 kg and contains a charge of+3.0 x 10 C. Show your work and/or explain your reasoning. (20 pts) 1. Now the same particle is removed from the thread and placed over the center of a charged plate. Are there any conditions under which it is possible for the particle to be suspended in the air above the plate? Show any relevant calculations and explain your reasoning. (10 pts) 2.Explanation / Answer
(1) in a static sitatuion net force is zero
Fnet=0
Fe+Fg=0
Fg is the gravitational force which is equal to -mg (minus sign due to downward)
Fe=Eq
Eq-mg=0
E=mg/q
E=(0.005x9.81)/(3.3x103)
E=1.48x10-4 N/C
Direction will be upwards
(2) If the charged plate is positive, then the electric field above the plate will be upwards
Eq=mg
The electric force will act in the upward direction
The particle will remain suspended in the air.
E=1.48 X 10-4 N/C