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3 marksElectric Fields

CAPE Physics Unit 2 · 2005 · Paper 1 · Question 2(b)(iii)

Figure IV shows a small light-conducting sphere supported by a long fine vertical nylon thread, suspended between two large metal plates connected to a high voltage d.c. supply.

When the ball is not touching either plate, the force on the ball is 0.05 N. The plates are 10 cm apart and the supply voltage is set to 1 kV. Calculate the charge on the sphere.

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Other parts of this question

  1. 2(a)(i)a)Write an expression for the electric field at B.[1 mark]
  2. 2(a)(i)b)Write an expression for the electric potential at B.[1 mark]
  3. 2(a)(ii)Show how the electric field and electric potential at B are related.[1 mark]
  4. 2(b)(i)Explain why the uncharged sphere is attracted to the positive plate.[1 mark]
  5. 2(b)(ii)Explain why the sphere subsequently oscillates between the plates.[3 marks]

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