posted by Trevor on .
A small plastic ball with a mass of 6.50x10^-3 kg and with a charge of +0.150x10^-6 C is suspended from an insulating thread and hangs between the plates of a capacitor. The ball is in equilibrium, whit the tread making an angle of 30 degrees with respect to the vertical. The area of each plate is 0.0150 m^2. What is the magnitude of the charge of each plate?
Are the capacitor plates horizontal or vertical or aligned tih the thread? How is the thread prevented from interfering with the capacitor plates?
They Are Vertical with the ball in between them.
dr wls is here now so there is hope.
Force down = m g = 6.5*10^-3 *9.8 = 53.7*10^-3 N
Force sideways = q E
where E = sigma/eo
so force sideways = q sigma/eo
tan 30 = (q sigma /eo)/53.7*10^-3
you know q, eo
so solve for sigma
charge = sigma * plate area
what does sigma represent?