Posted by Jenish on .
In a television picture tube, electrons are accelerated by thousands of volts through a vacuum. If a television set were laid on its back, would electrons be able to move upward against the force of gravity? What potential diffrence , acting over a distance of 3.0 cm, would be needed to balance the downward force of gravity so that an electron would remain stationary? Assume that the electric field is uniform.

Physics 
drwls,
The electric force on an electron is e V/d, where e is the electron charge and d is the separation. (V/d is the E field strength). To balance the gravitational force on Earth,
e V/d = m g
where g is the acceleration of gravity and m is the electron mass.
Solve for V = m g d/e
You should find the weightbalancing voltage to be very small compared to the actual TV picture tube voltage