The experiment involved the study of the relationship between electrostatic force and its counterforce which was the torque on a movable ball held a distance away from a charged ball. The aim of the experiment was to identify the quantitative relationship between electrostatic force (F) and the distance between the two balls(r). The expected theoretical result is that the distance of separation between the balls is indirectly proportional to electrostatic force.
Two charged spheres are used for this experiment. One is mounted on an insulating rod , counterbalanced and hanging on a thin torsion wire. The other sphere is mounted on a slide assembly and its distance to the fixed sphere is varied while the charge on the balls is maintained at a constant. The electrostatic force during charging is inversely proportional to the distance of separation .Mathematically, this is written as FEra where (a) is an unknown factor of distance. The charge induced on the mobile ball will be directly proportional to the angle of torsion (th). The relationship between angle theta and the distance can then be mathematically determined using data from lab experiment. At the end of the experiment one should have obtained the value of (ra) which is the distance between spheres at which electrostatic force counteracts torque and the held ball does not rotate about its wire.
1.Record the diameters of the two balls using a Vernier Caliper taking into consideration the percentage of uncertainty.
2.Pass the aluminum counterweight through the magnets of the electromagnetic dumper and ensure that the ball and the torsion wire rotate easily unhindered on their horizontal planes.
3.Adjust the angular dial on the torsion wire until the ball assembly mark rests on the fixed point as the aluminum counterweight mark does.
4.Touch the graphite painted ping-pong ball to the first ball and hence determine what the appropriate distance of separation is while they are touching.
5.Plug in the High Voltage Power Supply and adjust its knob counterclockwise to the maximum ensuring that it is switched off and that it is plugged into a 120 Volt mains supply.
6.Insert two High Voltage leads one into the rightmost of the three sockets and the other into the left most of the three sockets of the High Voltage Power Supply.
7.Turn the switch to on and the voltage to 6000 volts.
8.Hold the two balls an appropriate distance of 20 cm from one another, touch the first one then the other with the High Voltage leads for charging.
9.Mantain the charge applied on the balls (q) the same throughout the experiment.
10.Vary the distances to 6 cm apart and record the angle of displacement(thR) on the mobile ball using a protractor. Remember to realign the dial with the fixed counterweights mark recording the angle on the dial(thD).
11.Double the distance and repeat the charging, measuring and discharging for ten times noting down the values of the angle of the dial (th)
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