Fig. 22.1
The plates are connected to a power supply. The potential difference V between the plates is constant. The magnitude of the charge on each plate is Q. The separation between the plates is d.
Fig. 22.2 shows the variation with d of the charge Q on the positive plate.
Fig. 22.2
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Fig. 22.3
The plates are fixed and connected to a variable power supply. The weight of the oil drop is 1.8 × 10–14 N.
FE = ...................................... N [1]
a = .................................... ms–2 [3]
Fig. 22.4
The two vertical metal plates are connected to a high-voltage supply.
The foil is given a positive charge by briefly touching it to the positive plate.
The angle θ made with the vertical by the foil in the electric field is given by the expression
where q is the charge on the foil, E is the electric field strength between the plates and W is the weight of the foil.
The angle θ can be determined by taking photographs with the camera of a mobile phone.
Describe how the student can safely conduct an experiment to investigate the relationship between θ and E.
Identify any variables that must be controlled.
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