The sphere oscillates by hitting the two plates in turns.
8. Adjust the EHT to 3.5 kV. Observe and describe the motion of the charged sphere.
The sphere oscillates faster.
Results and Discussion
1. Explain the motions of the uncharged and charged conducting sphere when placing between two parallel charged metal plates.
Placing the uncharged sphere inside an electric field is to allow charges to be induced on
two opposite sides of the sphere. Thus the electrostatic forces acting on the sphere are
balanced so that the sphere remains motionless at its initial position.
If the sphere touches the positive plate, the sphere becomes positively charged and
immediately is attracted by the negative plate. The sphere is moving rapidly towards the
negative plate and can overcome the electrostatic force, eventually hitting the plate. For
the same reason, the sphere would return to hit the positive plate. Hence, the sphere
oscillates between the two plates by hitting the two plates. The same result will be
obtained when the sphere touches the negative plate firstly.
2. Explain the change(s) of the motion of the charged conducting sphere when the voltage across the parallel charged metal plates is increased.
The frequency of oscillation is increased when the voltage across the plates is getting
large. It is because the electric field is directly proportional to the voltage. Stronger the
electric field, the larger the electric force acting on the sphere. As a result, the sphere
moves faster.
3. Why we need to connect the negative terminal of EHT supply to the ground socket?
When the negative terminal connects to the ground socket, this enables the positive
terminal to attain its required positive voltage.
4. State the sources of error and suggest improvements for this experiment.
It must be sure that the sphere is neutral before placing it between the plates. This can be
done by discharging the sphere to the earth and carefully isolate to its surroundings.
5. Give a conclusion to this experiment.
The existence of electrostatic force in electric filed can be examined by the shuttling ball
experiment.
New Way Physics for Advanced Level
