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4 marksCapacitors

CAPE Physics Unit 2 · May/June 2021 · Paper 2 · Question 1(c)(i)

The time constant for the type of discharge curve obtained in (b) may be defined as the time taken for the current to decay to 1/e of its initial value (where e is Euler's number, the mathematical constant which is the base of natural logarithms). Use this definition and the graph drawn in Figure 2 to find the time constant of the circuit in Figure 1.

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Other parts of this question

  1. 1(a)(i)Describe the procedure involved in storing a quantity of electric charge on an initially uncharged parallel plate capacitor.[3 marks]
  2. 1(a)(ii)Explain the movement of charges in the procedure described in (a) (i).[3 marks]
  3. 1(b)On the grid provided in Figure 2 on page 7, plot a graph of the discharge current, I_D, versus time, t. Draw a smooth curve through the points.[4 marks]
  4. 1(c)(ii)Calculate the value of the unknown capacitor in Figure 1.[2 marks]
  5. 1(c)(iii)Calculate the charge on the capacitor before the switch is closed.[5 marks]
  6. 1(c)(iv)The capacitor consists of two metal plates separated by a layer of insulating material 0.5 mm thick and of dielectric constant 450. Determine the area of the…[5 marks]
  7. 1(d)Show, by equating the work per unit charge in moving a positive test charge q from B to A, that E, the strength of the uniform field between A and B, is equal…[4 marks]

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