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7.1 In an experiment to verify the relationship between the electrostatic force, FE, and distance, r, between two identical, positively charged spheres, the graph below was obtained.
7.1.1 State Coulomb’s law in words. (2)
7.1.2 Write down the dependent variable of the experiment. (1)
7.1.3 What relationship between the electrostatic force FE and the square of the distance, r2, between the charged spheres can be deduced from the graph? (1)
7.1.4 Use the information in the graph to calculate the charge on each sphere. (6)
7.2 A charged sphere, A, carries a charge of – 0,75 µC.
7.2.1 Draw a diagram showing the electric field lines surrounding sphere A. (2)
Sphere A is placed 12 cm away from another charged sphere, B, along a straight line in a vacuum, as shown below. Sphere B carries a charge of +0,8 μC. Point P is located 9 cm to the right of sphere A.
7.2.2 Calculate the magnitude of the net electric field at point P. (5)
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